bluuebunny/crossref_metadata_2025 huggingface dataset:
The Susceptibility of CA1 Pyramidal Cells to Cerebral Ischemia is Maintained after Neonatal, Lesion-Induced Reorganization of the Hippocampal Circuitry
Authors: Tønder Niels , Johansen Flemming F. , Zimmer Jens , Diemer Nils H.
Published: April 2011

Acute lesions of hippocampal pathways have been shown previously to ameliorate CA1 pyramidal cell loss after subsequent transient cerebral ischemia. In this study, we examined the effect of chronic neonatal lesion with reorganization of hippocampal circuitry on adult postischemic neuron loss in the hippocampus. Newborn rats were subjected to unilateral knife-cut lesions at various positions along the trisynaptic entorhino-dentatohippocampal pathway. Seven months later, the rats were subjected to transient cerebral ischemia using the four-vessel occlusion technique. At the time of killing 4 days later, a Nissl stain was used to demonstrate neuronal degeneration, while connective reorganization resulting from the neonatal lesions was monitored by Timm staining. In one group of rats, neonatal lesions had caused severe depletion of entorhinal projections to the septodorsal fascia dentata and hippocampus (CA1 and CA3), without any direct damage to the dorsal hippocampus itself. Another group had extensive damage of the dorsal CA3, with removal of the Schaffer collaterals from these levels to CA1, and variable damage to the entorhinal afferents. In both groups, the extent and pattern of ischemia-induced degeneration of CA1 pyramidal cells were the same on the lesioned and nonlesioned sides of the brain, demonstrating that neonatal lesions and the subsequent connective reorganization did not have a sparing effect. Seen in relationship to previous observations in adult rats of the neuroprotective actions of acute, preischemic lesions of the trisynaptic hippocampal pathway, it is concluded that CA1 pyramidal cell loss requires the presence of intact excitatory afferents rather than an intact hippocampal circuitry.
Elevation of Plasma Nitric Oxide End Products during Focal Cerebral Ischemia and Reperfusion in the Rat
Authors: Kumura Eiji , Kosaka Hiroaki , Shiga Takeshi , Yoshimine Toshiki , Hayakawa Toru
Published: April 2011

We investigated the alterations in the stable end products of nitric oxide, i.e., nitrate and nitrite, in the plasma during and after rat focal cerebral ischemia by an automated procedure based on the Griess reaction. At 2 h of middle cerebral artery (MCA) occlusion, plasma nitrate/nitrite levels were significantly higher (53 ± 8 μ M, mean ± SD, n = 5, p < 0.05) than in rats with sham operation (36 ± 9 μ M, n = 5), and were mildly elevated at 4 h of MCA occlusion (42 ± 9 μ M, n = 5, n.s.). At 30 min of reperfusion after 2 h of MCA occlusion, plasma nitrate/nitrite levels were more markedly elevated (72 ± 7 μ M, n = 5, p < 0.01 vs. sham operation), but were moderately elevated at 2 h of reperfusion after 2 h of MCA occlusion (61 ± 10 μ M, n = 5, p < 0.05). Plasma nitrite levels were not changed during these experimental periods. Administration of 20 mg/kg of NG-nitro-l-arginine methyl ester (l-NAME) significantly decreased plasma nitrate/nitrite as well as nitrite at 30 min of reperfusion after 2 h of MCA occlusion ( n = 5), but 2 mg/kg of l-NAME did not ( n = 3). The effect of 20 mg/kg of l-NAME on plasma nitric oxide end products was reversed by the simultaneous administration of 200 mg/kg of l-arginine ( n = 3), but not d-arginine ( n = 3). The present study suggests that the l-arginine-nitric oxide pathway is activated during acute cerebral ischemia and reperfusion.
Postischemic Administration of AK275, a Calpain Inhibitor, Provides Substantial Protection against Focal Ischemic Brain Damage
Authors: Bartus Raymond T. , Baker Keith L. , Heiser Angie D. , Sawyer Sean D. , Dean Reginald L. , Elliott Peter J. , Straub Julie A.
Published: April 2011

Experiments were conducted to determine whether a potent, reversible calpain inhibitor could reduce the cortical ischemic brain damage associated with focal ischemia in the rat. AK275 (Z-Leu–Abu–CONH–CH2CH3), the active isomer of the diastereomeric mixture, CX275, was employed in conjunction with a novel method of perfusing drug directly onto the infarcted cortical surface. This protocol reduced or eliminated numerous, nonspecific pharmacokinetic, hemodynamic, and other potentially confounding variables that might complicate interpretation of any drug effect. Focal ischemia was induced using a variation of the middle cerebral artery occlusion method. These studies demonstrated a reliable and robust neuroprotective effect of AK275 over the concentration range of 10 to 200 μ M (perfused supracortically at 4 μl/h for 21 h). Moreover, a 75% reduction in infarct volume was observed when initiation of drug treatment was delayed for 3 h postocclusion. Our data further support an important role of calpain in ischemia-induced neuropathology and suggest that calpain inhibitors may provide a unique and potentially powerful means of treating stroke and other ischemic brain incidents.
Alterations in τ Immunostaining in the Rat Hippocampus following Transient Cerebral Ischemia
Authors: Geddes James W. , Schwab Claudia , Craddock Susan , Wilson Janice L. , Pettigrew L. Creed
Published: April 2011

Previous studies in gerbils have shown that cytoskeletal disruption and a loss of the dendritic microtubule-associated protein, MAP2, may occur after short periods of transient global ischemia. τ, a predominantly axonal microtubule-associated protein, has not been examined following ischemia. We compared neuronal damage with alterations in MAP2, τ, and 72-kD heat shock protein (HSP72) immunostaining at various reperfusion times following 20 min of ischemia in the rat four-vessel occlusion model. τ accumulated in neuronal cell bodies throughout the hippocampal formation 30 min to 2 h after the ischemic insult. Perikaryal τ immunostaining was transient in most regions, but persisted in polymorphic hilar neurons. This was accompanied by a loss of immunostaining in the target of many hilar neurons, the inner molecular layer of the dentate gyrus. The same neuronal populations that exhibited increased τ immunostaining of perikarya later displayed an induction of HSP72 immunoreactivity. In contrast, loss of MAP2 immunostaining was not consistently observed before neuronal death and did not correspond to HSP72 induction. The altered τ immunostaining is not the direct result of excitotoxic insult, as intrahippocampal injection of kainic acid did not cause the somal accumulation of τ, but did cause disruption of MAP2 immunostaining. Taken together, the results suggest that the somal accumulation of τ is an early, sensitive, and selective marker of ischemic insult.
Temporal Profiles of Accumulation of Amyloid β/A4 Protein Precursor in the Gerbil after Graded Ischemic Stress
Authors: Tomimoto Hidekazu , Wakita Hideaki , Akiguchi Ichiro , Nakamura Shinichi , Kimura Jun
Published: April 2011

The neurons that accumulate β/A4 amyloid protein precursor (APP) after transient cerebral ischemia were characterized by comparing their distribution with those destined to suffer delayed neuronal death or those with induction of 72-kDa heat-shock protein. With immunohistochemistry of APP in gerbil brains, no alterations were detected after ischemia for 2 min and subsequent reperfusion for up to 7 days, whereas after ischemia for 3 min and reperfusion for 48 h, a small number of neurons, intensely immunoreactive for APP, were found to be scattered in the CA1 subfield of the hippocampus and the layer V/VI of the frontoparietal cortex. After reperfusion for 24 h following ischemia for 5 or 15 min, a large number of densely stained neurons appeared in the subiculum, and CA3 subfield of the hippocampus, and layers III and V/VI of the frontoparietal cortex. The majority of these neurons did not undergo delayed neuronal death after reperfusion for 72 h and thereafter. APP and heat-shock protein were upregulated in the same regions, but mostly in distinct neurons. These results indicate that APP accumulates in the neurons marginating the regions destined to die, and the majority of these neurons seem to survive after ischemic insult.
Blockade of Nitric Oxide Synthesis Inhibits Hippocampal Hyperemia in Kainic Acid-Induced Seizures
Authors: Rigaud-Monnet Anne-Sophie , Pinard Elisabeth , Borredon Josiane , Seylaz Jacques
Published: April 2011

We investigated whether the nitric oxide (NO) synthase inhibitor NG-nitro-l-arginine methyl ester (l-NAME) affects the cerebrovascular changes occurring in seizures induced by kainic acid (KA) in awake, spontaneously breathing rats. Blood flow and tissue Po2 and Pco2 were continuously and simultaneously measured by mass spectrometry from a cannula chronically implanted into the dorsal hippocampus. l-NAME (20 mg/kg; n = 8) or saline (n = 9) was administered i.p. 30 min prior to i.p. KA (10 mg/kg) injection. l-NAME significantly decreased hippocampal blood flow and Po2 and increased mean arterial blood pressure (MABP). In l-NAME-treated rats, seizure activity occurred about 10 min sooner than in control rats, and status epilepticus was inevitably followed by a flat electroencephalogram and sudden death. In contrast, control rats survived KA-induced seizures. Hippocampal blood flow was significantly less elevated during the seizures in l-NAME-treated rats than in control rats (maximal levels, 170 and 450%, respectively, of baseline values), though MABP remained significantly higher. Hippocampal Po2 was significantly decreased at all times after KA injection in l-NAME-treated rats, whereas it remained at or above normoxic levels in control rats. The present results show that l-NAME markedly attenuates the hippocampal blood flow and tissue Po2 changes in response to enhanced metabolic activity due to limbic seizures and suggest that NO is of major importance in cerebral blood flow control during KA-induced seizures.
Evaluation of Lactate Production and Clearance Kinetics by 1H NMR in a Model of Brief Repetitive Cerebral Ischemia
Authors: Hetherington Hoby P. , Tan Min-Jie , Luo Kang-Li , Pohost Gerald M. , Halsey James H. , Conger Karl A.
Published: April 2011

Pilots of high-performance aircraft are subject to repeated transient cerebral ischemia during high-gravitational stress maneuvers. Previously we have demonstrated that repeated episodes of transient cerebral ischemia and reflow are cumulative and lactate accumulations appear to be exponential. To evaluate the metabolic events determining the kinetics of lactate accumulation, and therefore the rates of substrate utilization, we have used in vivo 1H nuclear magnetic resonance with a 5-s time resolution to measure lactate production and clearance. The individual rates for each animal were then used to predict the accumulation of lactate in the same animal during 30 episodes of ischemia and reflow. Lactate accumulation was modeled as the balance between a zero-order production process during the ischemic period and a first-order clearance process. The predicted lactate accumulation showed excellent agreement with the observed time course, validating the predictive power of the simple model used. The highly reproducible nature of this model and its accuracy in predicting lactate accumulation should enable more accurate studies of the deleterious effects of lactate accumulation in cerebral ischemia by providing a highly reproducible means for generating a specific level of lactate accumulation.
Methodological Aspects of Brain Activation Studies: Cerebral Blood Flow Determined with [15O]Butanol and Positron Emission Tomography
Authors: Ingvar Martin , Eriksson Lars , Greitz Torgny , Stone-Elander Sharon , Dahlbom Magnus , Rosenqvist Goran , Trampe Peter af , von Euler Curt
Published: April 2011

In this methodological study, a procedure for measuring regional CBF (rCBF) with positron emission tomography and 15O-labelled tracers is optimized. Four healthy volunteers were subjected to eight studies with use of [15O]butanol as a tracer: four times while reading aloud and four times while reading silently from a phonologically balanced list of single words. The gain from these repeated intra-individual studies of the same activation state (fractionation) was demonstrated in terms of noise-equivalent counts in a phantom study. A computerized brain atlas was used to reformat the images to a common anatomical representation, thereby minimizing the effects of inter- and intra-individual anatomical and positional variations. This allowed the formation of inter- and intra-individual average subtraction images with error estimates. Differences between the two activation states were detected with use of an exploratory significance map based on a paired Student's t test. The results compared well with Friston's method of determining levels of statistical significance. No difference was obtained when comparing results from rCBF images and images generated from measurement of uptake of the tracer. The paradigm chosen for activation was shown to yield a constant activation level during the repeated measurements (i.e., no habituation).
Enhanced Detection in Brain Activation Maps Using a Multifiltering Approach
Authors: Poline Jean-Baptiste , Mazoyer Bernard M.
Published: April 2011

Current methods for detecting activation foci in positron emission tomography difference images include a low pass filtering step aimed at improving the signal-to-noise ratio. However, we show that detection sensitivity depends both on the activation signal and the filter sizes. Therefore, we propose to improve current detection methods by using a multifiltering strategy that is shown to be more sensitive when various kinds of signals are present in the brain activation images.
The Distribution and Kinetics of [18F]6-Fluoro-3-O-Methyl-l-Dopa in the Human Brain
Authors: Wahl Lindi , Chirakal Raman , Firnau Gunter , Garnett E. Stephen , Nahmias Claude
Published: April 2011

The analysis of positron tomographic studies of 3,4-dihydroxyphenylethylamine (dopamine) metabolism in which [18F]6-fluoro-l-3,4-dihydroxyphenylalanine (F-dopa) is used as a tracer is confounded by the presence of [18F]6-fluoro-3- O-methyl-l-3,4-dihydroxyphenylalanine (OMFD). This labeled molecule, formed by the action of peripheral cathechol- O-methyltransferase on F-dopa, crosses the blood–brain barrier and contributes to the radioactivity measured by the tomograph. Corrections for this radioactivity in the brain have been proposed. They rely upon the assumption that regional variations in the handling of this molecule by the brain are negligible. Although this assumption is pivotal for the proper quantification of dopamine metabolism using F-dopa, the distribution and kinetics of OMFD have never been studied in humans. We present results in humans that show that there is little selective regional 18F accumulation in the brain, that the distribution volume of OMFD is close to unity, and that a single, reversible compartment is adequate to model the measured time course of radioactivity after an OMFD injection. Analysis of plasma samples for labeled metabolites showed that more than 95% of the radioactivity was associated with OMFD at all times. Our results for OMFD kinetics are in accord with published results obtained in nonhuman primates and for the bidirectional transport of large neutral amino acids across the blood-brain barrier measured using a synthetic amino acid. However, our results also indicate that there are small but significant differences in OMFD kinetics in different parts of the brain that may prevent inferences about the handling of OMFD in one part of the brain from being extended to other parts of the brain.
Widespread Attenuation of the Cerebrovascular Reactivity to Hypercapnia following Inhibition of Nitric Oxide Synthase in the Conscious Rat
Authors: Bonvento Gilles , Seylaz Jacques , Lacombe Pierre
Published: April 2011

Despite the increasing number of publications devoted to the cerebrovascular role of NO, its precise influence in awake animals is still poorly characterized. The effect of nitric oxide synthase (NOS) inhibition on the cerebrovascular CO2 reactivity was therefore studied in conscious rats. Regional CBF was measured using the [14C]iodoantipyrine technique and brain tissue sampling. The CO2 reactivity was determined 60 min after administration of 30 mg kg−1 Nω-nitro-l-arginine methyl ester (l-NAME). Blockade of NOS by l-NAME significantly decreased CBF in all 11 brain regions studied (−17 to −49%) and increased arterial pressure from 117 ± 12 to 147 ±11 mm Hg. In control conditions, CO2 responsiveness ranged from 1.3 ± 0.4 in the hypophysis to 6.4 ± 0.6 ml 100 g−1 min−1 mm Hg−1 in the parietal cortex. Following l-NAME injection, the reactivity to hypercapnia was significantly attenuated in all structures, the magnitude of the reduction ranging from 57% in the medulla to 74% in the cerebellum. This result shows that NO is an important mediator of the hypercapnic vasodilation in the conscious rat.
NMR Imaging of the Apparent Diffusion Coefficient (ADC) for the Evaluation of Metabolic Suppression and Recovery after Prolonged Cerebral Ischemia
Authors: Hossmann Konstantin-Alexander , Fischer Matthias , Bockhorst Kurt , Hoehn-Berlage Mathias
Published: April 2011

Adult normothermic cats were submitted to 1-h complete cerebrocirculatory arrest by intrathoracic occlusion of the internal mammary, the innominate, and the subclavian arteries in combination with pharmacologically induced hypotension. After ischemia, recirculation was initiated at different blood pressure levels to manipulate the postischemia resuscitation conditions. The resulting spectrum of postischemic recovery was studied by combining nuclear magnetic resonance imaging of the apparent diffusion coefficient (ADC) with pictorial assays of brain tissue pH, ATP, glucose, and lactate. Before ischemia, the mean ADC (average of seven coronal slices of five cats) was 713 ± 40 × 10−6 mm2/s. After 10-min ischemia, ADC declined to 68% of control and after 50 min slightly further to 63% of control. During recirculation after 1-h ischemia, recovery of ADC varied depending on the initial reperfusion pressure and other systemic variables. In two animals ADC only transiently increased followed by a secondary decline below the postischemic level. In three other animals ADC returned to near control within 1 h of recirculation. The comparison of ADC changes with previously reported changes in extracellular volume revealed a close relationship, supporting the notion that ADC is a function of the intra/extracellular water compartmentation. Recovery of ADC correlated closely with tissue pH and metabolic recovery, studied 3 h after the initiation of recirculation. Animals without recovery of ADC exhibited global depletion of ATP and glucose and severe lactacidosis, whereas animals with recovery of ADC showed replenishment of ATP and glucose to near control and a substantial reversal of lactacidosis. Our data demonstrate that imaging of ADC provides reliable information about the metabolic state of the brain and can be used to monitor, with high temporal and regional resolution, the manifestation and reversal of ischemic brain injury.
The Effect of Hypothermia on Transient Focal Ischemia in Rat Brain Evaluated by Diffusion- and Perfusion-Weighted NMR Imaging
Authors: Jiang Q. , Chopp M. , Zhang Z. G. , Helpern J. A. , Ordidge R. J. , Ewing J. , Jiang P. , Marchese B. A.
Published: April 2011

The effect of moderate whole-body hypothermia (30°C) on transient middle cerebral artery (MCA) occlusion in the rat was evaluated using diffusion- and perfusion-weighted magnetic resonance imaging. Two hours of transient MCA occlusion was induced by intracarotid insertion of a nylon filament under normothermic (n = 14) and hypothermic (n = 7) conditions. Diffusion- and perfusion-weighted imaging were performed before, during, and after focal ischemia from 30 min up to 7 days. In hypothermic animals, scattered neuronal necrosis was localized to select areas of the caudate putamen and the parietal and insular cortex. In contrast, the normothermic ischemic animals exhibited pan-necrosis and infarct encompassing the damaged area. The diffusion and perfusion data measured from caudate putamen indicate that hypothermia causes a significant reduction in the apparent diffusion coefficient of water (ADCw) and CBF values from normothermic control values (p < 0.01). In both normothermic and hypothermic animals after onset of MCA occlusion, ADCw and CBF values in the core of the ischemic region (striatum) significantly declined from the preischemic and homologous contralateral control ADCw and CBF values (p < 0.05). However, ADCw and CBF in the hypothermic group returned toward control more rapidly than in the normothermic group. These results suggest that the protective effect of hypothermia on ischemic cell damage is reflected in the early return of ADCw during reperfusion and the reduction of ischemic cell damage by hypothermia may be mediated by the improved CBF during acute reperfusion.
Fast Nonsupervised 3D Registration of PET and MR Images of the Brain
Authors: Mangin Jean-François , Frouin Vincent , Bloch Isabelle , Bendriem Bernard , Lopez-Krahe Jaime
Published: April 2011

We propose a fully nonsupervised methodology dedicated to the fast registration of positron emission tomography (PET) and magnetic resonance images of the brain. First, discrete representations of the surfaces of interest (head or brain surface) are automatically extracted from both images. Then, a shape-independent surface-matching algorithm gives a rigid body transformation, which allows the transfer of information between both modalities. A three-dimensional (3D) extension of the chamfer-matching principle makes up the core of this surface-matching algorithm. The optimal transformation is inferred from the minimization of a quadratic generalized distance between discrete surfaces, taking into account between-modality differences in the localization of the segmented surfaces. The minimization process is efficiently performed via the precomputation of a 3D distance map. Validation studies using a dedicated brain-shaped phantom have shown that the maximum registration error was of the order of the PET pixel size (2 mm) for the wide variety of tested configurations. The software is routinely used today in a clinical context by the physicians of the Service Hospitalier Frédéric Joliot (>150 registrations performed). The entire registration process requires ∼5 min on a conventional workstation.
The Metabolic Topography of Parkinsonism
Authors: Eidelberg D. , Moeller J. R. , Dhawan V. , Spetsieris P. , Takikawa S. , Ishikawa T. , Chaly T. , Robeson W. , Margouleff D. , Przedborski S. , Fahn S.
Published: April 2011

We used [18F]fluorodeoxyglucose/positron emission tomography (18F-FDG/PET) and a statistical model of regional covariation to study brain topographic organization in parkinsonism. We studied 22 patients with Parkinson's disease (PD), 20 age-matched normal volunteers, and 10 age- and severity-matched patients with presumed striatonigral degeneration (SND). We used FDG/PET to calculate global, regional, and normalized metabolic rates for glucose (GMR, rCMRglc, rCMRglc/GMR). Metabolic parameters in the three groups were compared using an analysis of variance, with a correction for multiple comparisons, and discriminant analysis. The scaled subprofile model (SSM) was applied to the combined rCMRglc dataset to identify topographic covariance profiles that distinguish PD patients from SND patients and normals. GMR, rCMRglc, and rCMRglc/GMR were normal in PD; caudate and lentiform rCMRglc/GMR was reduced in the SND group ( p < 0.01). SSM analysis of the combined group of patients and normals revealed a significant topographic profile characterized by increased metabolic activity in the lentiform nucleus and thalamus associated with decreased activity in the lateral frontal, paracentral, inferior parietal, and parietooccipital areas. Individual subject scores for this profile were significantly elevated in PD patients compared with normals and SND patients ( p < 0.001) and discriminated the three groups. In the PD group, subject scores for this factor correlated with individual subject Hoehn and Yahr (H&Y) scores ( p < 0.02), and with quantitative rigidity ( p < 0.01) and bradykinesia ( p < 0.03) ratings, but not with tremor ratings. SSM analysis of right-left metabolic asymmetries yielded a topographic contrast profile that accurately discriminated mildly affected PD patients (H&Y Stage I) from normals. Our findings demonstrate that abnormal topographic covariance profiles exist in parkinsonism. These profiles have potential clinical application as neuroimaging markers in parkinsonism.
Tirilazad Pretreatment Improves Early Cerebral Metabolic and Blood Flow Recovery from Hyperglycemic Ischemia
Authors: Maruki Yuichi , Koehler Raymond C. , Kirsch Jeffrey R. , Blizzard Kathleen K. , Traystman Richard J.
Published: April 2011

Acidosis may augment cerebral ischemic injury by promoting lipid peroxidation. We tested the hypothesis that when acidosis is augmented by hyperglycemia, pretreatment with the 21-aminosteroid tirilazad mesylate (U74006F), a potent inhibitor of lipid peroxidation in vitro, improves early cerebral metabolic recovery. In a randomized, blinded study, anesthetized dogs received either tirilazad mesylate (1 mg/kg plus 0.2 mg/kg/h; n = 8) or vehicle (n = 8). Hyperglycemia (400–500 mg/dl) was produced prior to 30 min of global incomplete cerebral ischemia. Intracellular pH and high energy phosphates were measured by phosphorus magnetic resonance spectroscopy. During ischemia, microsphere-determined CBF decreased to 8 ± 4 ml min−1 100 g−1 and intracellular pH decreased to 5.6 ± 0.2 in both groups. During the first 20 min of reperfusion, ATP partially recovered in the vehicle group to 57 ± 21% of baseline, but then declined progressively in association with elevated intracranial pressure. By 30 min, ATP recovery was greater in the tirilazad group (77 ± 35 vs. 36 ± 19%), although postischemic hyperemia was similar. By 45 min, the tirilazad group had a higher intracellular pH (6.5 ± 0.5 vs. 5.9 ± 0.6) and a lower intracranial pressure (18 ± 6 vs. 52 ± 24 mm Hg). By 180 min, blood flow and ATP were undetectable in seven of eight vehicle-treated dogs, whereas ATP was >67% and pH was >6.7 in six of eight tirilazad-treated dogs. Thus, tirilazad acts during early reperfusion to prevent secondary metabolic decay associated with severe acidotic ischemia. If tirilazad acts by inhibiting lipid peroxidation, then these data are consistent with extreme acidosis limiting recovery by a mechanism involving lipid peroxidation.
Effects of Adrenomedullin, Calcitonin Gene-Related Peptide, and Amylin on Cerebral Circulation in Dogs
Authors: Baskaya Mustafa K. , Suzuki Yoshio , Anzai Masaoki , Seki Yukio , Saito Kiyoshi , Takayasu Masakazu , Shibuya Masato , Sugita Kenichiro
Published: April 2011

The effect of human adrenomedullin on cerebral circulation was investigated in dogs in vivo and in vitro. Bolus administration of adrenomedullin or its homologous peptides, calcitonin gene-related peptide (CGRP) and amylin, into the vertebral artery induced a dose-dependent increase in vertebral blood flow. The potencies of adrenomedullin and CGRP were similar and approximately 100 times more than that of amylin. The effects of adrenomedullin and CGRP were inhibited by CGRP8-37, an antagonist of CGRP. In contrast to substance P, adrenomedullin did not induce an increase in blood flow after prior administration of CGRP. Pretreatment with either NG-nitro-l-arginine methyl ester or indomethacin did not affect the adrenomedullin-induced increase in blood flow. Intracisternal administration of adrenomedullin induced dilation of the basilar and other major cerebral arteries in a dose-dependent manner, accompanied by an increase in the concentration of cyclic AMP in the cerebrospinal fluid. Adrenomedullin also induced relaxation of isolated basilar and middle cerebral arterial rings. These data suggest that adrenomedullin induces vasodilation of cerebral arteries and an increase in vertebral blood by acting at CGRP receptors positively coupled to adenylate cyclase, and that these effects are not dependent on nitric oxide or prostaglandin formation.
Inhibition of Acetylcholinesterase Modulates the Autoregulation of Cerebral Blood Flow and Attenuates Ischemic Brain Metabolism in Hypertensive Rats
Authors: Sadoshima Seizo , Ibayashi Setsuro , Fujii Kenichiro , Nagao Tetsuhiko , Sugimori Hiroshi , Fujishima Masatoshi
Published: April 2011

We designed the present study to examine whether or not the inhibition of acetylcholinesterase modulates cerebral microcirculation in hypotension and improves brain metabolism in ischemia induced by bilateral carotid artery occlusion in hypertensive rats. Blood flow to the parietal cortex was determined by the H2 clearance method. Lactate, pyruvate, and ATP were estimated by enzymatic methods. Acetylcholinesterase inhibitor (AChEI, ENA-713), at 0.05, 0.1, or 0.5 mg/kg, was intravenously injected 10 min before either hemorrhagic hypotension or cerebral ischemia. The levels of acetylcholine in the control were 29.3 ± 8.1 (mean ± SD) and 39.5 ± 8.1 pmol/mg in the cortex and hippocampus, respectively, and they were significantly decreased by 15–19% after 60 min of ischemia in the vehicle-treated rats.

AChEI preserved the levels to 93–98% of the control (p < 0.05 versus vehicle). The lower limit of autoregulation was 74 ± 9% of the resting values. The administration of AChEI helped preserve blood flow and lowered the limit to 64 ± 6% (p < 0.05 versus control). After 60 min of ischemia, lactate increased 6.5-fold and ATP decreased to 64% of the control value. The administration of AChEI dose-dependently reduced the lactate level 1.9- to 3.9-fold and well preserved the ATP level to 94–97% of the control. The inhibition of acetylcholinesterase activity may preserve cerebral autoregulation during hypotension and protect cerebral metabolism against ischemic insult.
Effect of Soluble Complement Receptor-1 on Neutrophil Accumulation after Traumatic Brain Injury in Rats
Authors: Kaczorowski Susan L. , Schiding Joanne K. , Toth Carol A. , Kochanek Patrick M.
Published: April 2011

As part of the acute inflammatory response, neutrophils accumulate in the central nervous system after injury. Recently, a soluble human recombinant complement receptor (sCR1; BRL 55730; T Cell Sciences, Inc., Cambridge, MA, U.S.A.) has been developed that inhibits the activation of both the classical and the alternative pathways of complement. sCR1 attenuates the effects of the acute inflammatory response in several models of injury outside the central nervous system. The role of complement in traumatic brain injury, however, remains undefined. We hypothesized that treatment with sCR1 would attenuate neutrophil accumulation in the brain after cerebral trauma. Using a randomized, blinded protocol, 18 anesthetized Sprague–Dawley rats were pretreated with sCR1 or saline (control) at both 2 h and 2 min before trauma (weight drop) to the exposed right parietal cortex. A third dose of sCR1 (or saline) was given 6 h after trauma. Coronal brain sections centered on the site of trauma were obtained at 24 h after trauma and analyzed for myeloperoxidase (MPO) activity as a marker of neutrophil accumulation. Complete blood counts with differential were obtained before treatment with sCR1 and at 24 h after trauma. At 24 h after trauma, brain MPO activity was reduced by 41% in sCR1-treated rats compared with control rats [0.1599 ± 0.102 versus 0.27(2 ± 0.178 U/g (mean ± SD); p = 0.02]. The neutrophil count in peripheral blood increased approximately twofold in both groups. Neutrophil accumulation occurring in the brain after trauma is inhibited by sCR1 treatment. This suggests that complement activation is involved in the local inflammatory response to traumatic brain injury and plays an important role in neutrophil accumulation in the injured brain.
Labeling of Metabolic Pools by [6-14C]Glucose during K+-Induced Stimulation of Glucose Utilization in Rat Brain
Authors: Adachi Keiji , Cruz Nancy F. , Sokoloff Louis , Dienel Gerald A.
Published: April 2011

[6-14C]Glucose is the tracer sometimes recommended to assay cerebral glucose utilization (CMRglc) during transient or brief functional activations, but when used to study visual stimulation and seizures in other laboratories, it underestimated CMRglc. The metabolic fate of [6-14C]glucose during functional activation of cerebral metabolism is not known, and increased labeling of diffusible metabolites might explain underestimation of CMRglc and also reveal trafficking of metabolites. In the current studies cerebral cortex in conscious rats was unilaterally activated metabolically by KCl application, and CMRglc was determined in activated and contralateral control cortex with [6-14C]glucose or 2-[14C]deoxyglucose ([14C]DG) over a 5- to 7-min interval. Local 14C concentrations were determined by quantitative autoradiography. Labeled precursor and products were measured bilaterally in paired cortical samples from funnel-frozen brains. Left-right differences in 14C contents were small with [6-14C]glucose but strikingly obvious in [14C]DG autoradiographs. CMRglc determined with [6-14C]glucose was slightly increased in activated cortex but 40–80% below values obtained with [14C]DG. [14C]Lactate was a major metabolite of [6-14C]glucose in activated but not control cortex and increased proportionately with unlabeled lactate. These results demonstrate significant loss of labeled products of [6-14C]glucose from metabolically activated brain tissue and indicate that [14C]DG is the preferred tracer even during brief functional activations of brain.
Three-Dimensional Imaging of Nitric Oxide Production in the Rat Brain Subjected to Ischemia—Hypoxia
Authors: Kuppusamy Periannan , Ohnishi S. Tsuyoshi , Numagami Yoshihiro , Ohnishi Tomoko , Zweier Jay L.
Published: April 2011

By the systemic administration of diethyldithiocarbamate and iron into the rat, nitric oxide radicals produced in the brain during ischemia–hypoxia were trapped. The right hemisphere of the brain was then removed and frozen with liquid nitrogen. With use of recently developed electron paramagnetic resonance imaging instrumentation and techniques, three-dimensional imaging of the production of the nitric oxide radicals in several brains was performed. The results suggest that nitric oxide radicals were produced and trapped in the areas that are known to have high nitric oxide synthase activity, such as cortex, hippocampus, hypothalamus, amygdala, and substantia nigra. In this ischemia–hypoxia model, which did not interrupt the posterior circulation, the production and trapping of nitric oxide in the cerebellum were ∼30% of those in the cerebrum.
A Dual Role for Nitric Oxide in NMDA-Mediated Toxicity in vivo
Authors: Globus Mordecai Y.-T. , Prado Ricardo , Sanchez-Ramos J. , Zhao Weizhao , Dietrich W. Dalton , Busto Raul , Ginsberg Myron D.
Published: April 2011

Nitric oxide has been implicated in N-methyl-d-aspartate (NMDA)-mediated damage in vitro; however, its role in excitotoxic damage in vivo is not clear. In the present study we evaluated the histopathological and hemodynamic consequences of intrastriatal injections of various doses of NMDA and determined the effects of nitric oxide synthase inhibition on these changes. NMDA was injected into the striatum at doses of 50, 150, and 300 nmol with or without Nω-nitro-l-arginine methyl ester (L-NAME; 100 μg, locally). Three days following injections histopathological assessment was performed by morphometric analysis of the lesion area in multiple sections taken from the anterior to the posterior borders of the lesion. In animals injected with 150 and 300 nmol of NMDA (±L-NAME), local CBF (lCBF) was determined 30 min following injections using 14C-iodoantipyrine autoradiography. All NMDA-treated animals showed a well-demarcated lesion extending beyond the injection site. The volume of the lesion correlated significantly with the NMDA dose injected. The effects of L-NAME on lesion size were dependent on the dose of the NMDA. The lesion induced by 50 nmol of NMDA was not affected by L-NAME. With a dose of 150 nmol of NMDA, L-NAME induced a 43% increase in lesion volume. In contrast, a 38% decrease in lesion size was observed in animals treated with 300 nmol of NMDA combined with L-NAME. At a dose of 150 nmol, NMDA induced a significant elevation in lCBF, which was restricted to regions close to the injection site including the center areas of the anterior and middle striatum. The increase in lCBF observed with 150 nmol of NMDA was significantly attenuated in the NMDA + L-NAME-treated group. The lCBF changes induced by 300 nmol of NMDA were not significantly different from those in the 150-nmol group; however, the extent of the regions involved was larger. The increases in lCBF were observed in all striatal regions including the central and peripheral areas. L-NAME did not have a significant effect on the lCBF changes induced by NMDA at a dose of 300 nmol. These data suggest that in vivo the involvement of nitric oxide in NMDA toxicity depends on the NMDA dose and on the participation of hemodynamic mechanisms secondary to NMDA exposure.
Effects of TNF-α on the Production of Vasoactive Substances by Cerebral Endothelial and Smooth Muscle Cells in Culture
Authors: Estrada Carmen , Gomez Carmen , Martin Carmen
Published: April 2011

The effects of tumor necrosis factor-α (TNF-α) on the production of the vasoactive substances nitric oxide (NO) and endothelin-1 (ET-1) were investigated in cerebrovascular cells in culture. Bovine cerebral endothelial cells (BCEC) stained positively for NADPH-diaphorase/NO synthase activity and spontaneously produced nitrite, a stable NO oxidation product, which accumulated in the culture medium in a linear way for 48 h. Low concentrations of TNF-α (0.5–2 ng/ml) significantly enhanced nitrite production after a 24-h incubation. Higher concentrations or longer exposure times resulted in a cytotoxic effect that altered cell morphology, released lactate dehydrogenase (LDH) to the culture medium, and reduced the protein content. Dexamethasone, but not the NO synthase inhibitor N-iminoethyl-l-ornithine (L-NIO), prevented the cytotoxic effect of TNF-α in BCEC. TNF-α also significantly enhanced nitrite production in bovine cerebral smooth muscle cells (BCSMC). The enhancement was detected at all times between 8 and 72 h and at all concentrations tested (2–100 ng/ml). Signs of cytotoxicity were not observed in BCSMC after incubation with TNF-α. ET-1 was constitutively secreted by BCEC. The production of ET-1 was stimulated by thrombin. TNF-α enhanced the release of ET-1 in BCEC, and this enhancement was not modified by the simultaneous addition of interferon-γ (IFN-γ). BCSMC did not produce ET-1, either spontaneously or in the presence of TNF-α, IFN-γ, or of both together. These effects of TNF-α on cerebrovascular cells may explain the microvascular alterations found in some inflammatory or traumatic conditions in which this cytokine is increased in the cerebral tissue.
Role of Neutrophils in Radical Production during Ischemia and Reperfusion of the Rat Brain: Effect of Neutrophil Depletion on Extracellular Ascorbyl Radical Formation
Authors: Matsuo Yoshiyuki , Kihara Tsuyoshi , Ikeda Masato , Ninomiya Mitsuyoshi , Onodera Hiroshi , Kogure Kyuya
Published: April 2011

A growing body of experimental data indicate that oxygen radicals may mediate the brain injury during ischemia–reperfusion. One potential source of oxygen radicals is activated neutrophils. To study the role of neutrophils in radical production during cerebral ischemia–reperfusion, we evaluated the effects of depletion of circulating neutrophils by administration of an anti-neutrophil monoclonal antibody (RP3) on radical formation in rats with 1-h middle cerebral artery (MCA) occlusion. In the present study, we employed a new electron spin resonance method coupled with brain microdialysis. The method uses the endogenous ascorbyl radical (AR) concentration as a marker of oxygen radicals and requires no spin-trapping agents. In the vehicle controls, extracellular AR decreased during MCA occlusion. After reperfusion, AR significantly increased at 30 min and 1 h, returned to near basal level until 2 h, and increased again at 24 h after reperfusion. In the rats treated with RP3, AR decreased during MCA occlusion to the same extent as in the vehicle control. However, RP3 treatment completely inhibited the increase in extracellular AR after reperfusion. RP3 treatment exerted no effect on the changes in extracellular ascorbate or tissue Po2 throughout the experimental period. In conclusion, neutrophils are a major source of oxygen radicals during reperfusion after focal cerebral ischemia.
Increase in Insulin-like Growth Factor II Receptor within Ischemic Neurons following Focal Cerebral Infarction
Authors: Stephenson Diane T. , Rash Karen , Clemens James A.
Published: April 2011

The mechanisms underlying the response of the brain to ischemia are not fully understood. Biochemical and morphological changes following neocortical infarction can be investigated in rats using a model of focal cerebral ischemia induced by unilateral occlusion of the middle cerebral artery (MCA). Evaluation of ischemic damage often employs conventional histologic stains. Immunocytochemistry can be used as a valuable tool in this model to define changes in specific proteins of interest. In this study, an antiserum raised against insulin-like growth factor II (IGF-II) receptor was used to evaluate changes of IGF-II receptor immunoreactivity in the cerebral cortex of rats 4 and 7 days following permanent MCA occlusion. IGF-II receptor immunoreactivity was found to be associated with neocortical pyramidal neurons within the core of the ischemic infarct itself. The staining intensity was markedly elevated above that observed in nonischemic neurons. Immunopositive neurons exhibited a punctate staining pattern. These neurons appeared to correspond to argentophilic neurons, as defined by modified Bielschowsky silver staining. Evaluation of other neuronal markers revealed the absense of immunoreactivity for neuron-specific enolase and for tyrosine hydroxylase within the ischemic area. These observations show an increase in a specific growth factor receptor within neurons in the ischemic core of a focal infarct several days following permanent focal infarction, a time when neurons are presumed to be dead. The significance and the potential role of IGF-II receptor in lesion-induced plasticity are discussed.
Regional Alterations of ATP and Heat-Shock Protein-72 mRNA following Hypoxia—Ischemia in Neonatal Rat Brain
Authors: Kobayashi Shuichi , Welsh Frank A.
Published: April 2011

Neonatal rats, 7 days of age, underwent unilateral carotid artery ligation followed by exposure to hypoxia (8% O2) for 80 min. At the end of the period of hypoxia, and after recovery for 2 or 24 h, regional levels of ATP and heat-shock protein-72 (hsp72) mRNA were measured in adjacent brain sections using ATP-luminescence histochemistry and in situ hybridization, respectively. At the end of hypoxia, ATP levels were decreased in a patchy pattern within the hemisphere ipsilateral to the carotid ligation. In the parietal cortex, the reduction of ATP often occurred in columns oriented perpendicular to the cortical surface. Expression of hsp72 mRNA was not detected prior to recovery, except in the ventricular lining of the ipsilateral hemisphere. However, by 2 h of recovery, hsp72 mRNA was expressed in a diffuse pattern in the ipsilateral hemisphere, even in regions in which the distribution of ATP remained patchy. Although the regional extent of expression varied in different animals, hsp72 mRNA was expressed consistently in the subcortical white matter, which, in some animals, was the only region showing expression. In contrast to the diffuse pattern of expression at 2 h of recovery, expression of hsp72 mRNA at 24 h was highly localized in the superficial layers of cerebral cortex and the pyramidal cell layer of hippocampus. The present results demonstrate that hypoxia–ischemia causes regionally distinct alterations in ATP and hsp72 mRNA that may be related to cell injury in this model.
Reduced Local Cerebral Blood Flow in Periventricular White Matter in Experimental Neonatal Hydrocephalus—Restoration with CSF Shunting
Authors: da Silva Marcia C. , Michowicz Shalom , Drake James M. , Chumas Paul D. , Tuor Ursula I.
Published: April 2011

The extent to which the reduction in CBF occurring in hydrocephalus is a primary or secondary event in the pathogenesis of the brain injury that ensues has not been clearly established. This is particularly true in neonatal hydrocephalus, where the disorder is most common, and where timing of the treatment of the developing nervous system is so important. We investigated the changes in local CBF (lCBF) in an animal model of severe progressive neonatal hydrocephalus before and after CSF shunting. Hydrocephalus was induced in 27 1-week-old kittens by percutaneous injection of 0.05 ml of 25% kaolin into the cisterna magna. Fourteen littermates acted as controls. The lCBF was measured by 14C-iodoantipyrine quantitative autoradiography after 1 week in 15 animals (8 hydrocephalic, 7 controls) and after 3 weeks in 26 animals (19 hydrocephalic, 7 controls) following induction of hydrocephalus. Twelve of the 3-week hydrocephalic group received a ventriculoperitoneal shunt 10 days following kaolin injection. At 1 week following induction of hydrocephalus, lCBF was globally reduced in cortical gray matter and white matter as well as deep subcortical structures. The maximum reduction was in the parietal white matter, to 37% of control levels. At 3 weeks a significant reduction in lCBF persisted only in the white matter (parietal, occipital, and corpus callosum; average, 42% of control levels), whereas cortical gray and deep subcortical structures had returned to normal levels spontaneously. lCBF was normal in 3-week hydrocephalic shunted animals in all areas. CSF shunting restores the fall in lCBF in the periventricular white matter in this model. These findings are consistent with previous studies in the same model demonstrating derangement of high-energy phosphate metabolism and white matter anaerobic glycolysis with hydrocephalus and resolution with shunting.