bluuebunny/crossref_metadata_2025 huggingface dataset:
N-Acetylaspartate as an in vivo Marker of Neuronal Viability in Kainate-Induced Status Epilepticus: 1H Magnetic Resonance Spectroscopic Imaging
Authors: Ebisu Toshihiko , Rooney William D. , Graham Steven H. , Weiner Michael W. , Maudsley Andrew A.
Published: April 2011

N-acetylaspartate (NAA) has been proposed as a marker of neuronal density. Therefore, regional measurement of NAA by magnetic resonance spectroscopic imaging (MRSI) may provide a sensitive method for detection of selective neuronal loss, in contrast to conventional imaging techniques such as magnetic resonance imaging (MRI). To test this hypothesis, we produced selective neuronal injury by kainate-induced status epilepticus. Three days later three-dimensional 1H-MRSI was obtained and compared with conventional T2-weighted MRI and histological findings in normal and kainatetreated rats. Reduction of NAA determined by MRSI in piriform cortex, amygdala, and hippocampus correlated well with neuronal injury determined from histology. Changes of NAA, without any MRI changes in hippocampus, indicated greater sensitivity of MRSI for detection of neuronal injury. These results are consistent with the hypothesis that reduction of NAA measured by MRSI may be a sensitive marker of neuronal injury in vivo in a variety of disease states.
Effects of Timing and Duration of Cognitive Activation in [15O]Water PET Studies
Authors: Hurtig Richard R. , Hichwa Richard D. , O'Leary Daniel S. , Ponto Laura L. Boles , Narayana Shalini , Watkins G. Leonard , Andreasen Nancy C.
Published: April 2011

The multiple injection [15O]water method offers unique opportunities for studying cognitive processing by the human brain. The influence of the duration and temporal placement of an activation task, in relation to the arrival of the radiotracer in the brain, is a fundamental methodologic question for cognitive activation studies. A quantitative positron emission tomography (PET) study of five normal volunteers was performed in which the stimulation consisted of a visual activation task (alternating checkerboard pattern) superimposed on an auditory baseline task (syllable monitoring). Ten injection conditions, with varying duration and timing of the visual activation, were used. Regional CBF (rCBF) in visual cortex was measured quantitatively using the autoradiographic method. A 20-s stimulation, centered on the bolus arrival in the brain, produced significant changes in rCBF. Because varying the duration and timing of the activation task technically violates the temporal homogeneity assumption of the autoradiographic model, a mathematical simulation was formulated to evaluate the potential influence of these variations. Results of the simulation are consistent with the PET data and suggest that activation can be limited to a narrow temporal window centered on the radiotracer uptake. The ability to observe significant changes in rCBF with short stimulation intervals is of particular interest in the use of [15O]water PET for studies of cognitive processes with a short time course.
SPECT Quantification of [123I]Iomazenil Binding to Benzodiazepine Receptors in Nonhuman Primates: II. Equilibrium Analysis of Constant Infusion Experiments and Correlation with in vitro Parameters
Authors: Laruelle Marc , Abi-Dargham Anissa , AI-Tikriti Mohammed S. , Baldwin Ronald M. , Zea-Ponce Yolanda , Zoghbi Sami S. , Charney Dennis S. , Hoffer Paul B. , Innis Robert B.
Published: April 2011

In vivo benzodiazepine receptor equilibrium dissociation constant, KD, and maximum number of binding sites, Bmax, were measured by single photon emission computerized tomography (SPECT) in three baboons. Animals were injected with a bolus followed by a constant i.v. infusion of the high affinity benzodiazepine ligand [123I]iomazenil. Plasma steady-state concentration and receptor–ligand equilibrium were reached within 2 and 3 h, respectively, and were sustained for the duration (4–9 h) of the experiments (n = 15). At the end of the experiments, a receptor saturating dose of flumazenil (0.2 mg/kg) was injected to measure nondisplaceable activity. Experiments were carried out at various levels of specific activity, and Scatchard analysis was performed for derivation of the KD (0.59 ± 0.09 n M) and Bmax (from 126 n M in the occipital region to 68 n M in the striatum). Two animals were killed and [125I]iomazenil Bmax and KD were measured at 22 and 37°C on occipital homogenate membranes. In vitro values of Bmax (114 ± 33 n M) and 37°C KD (0.66 ± 0.16 n M) were in good agreement with in vivo values measured by SPECT. This study demonstrates that SPECT can be used to quantify central neuroreceptors density and affinity.
Effect of Delayed Thrombolysis with rt-PA in a Rat Embolic Stroke Model
Authors: Overgaard Karsten , Sereghy Tomas , Pedersen Hans , Boysen Gudrun
Published: April 2011

The effect of delayed thrombolysis with recombinant tissue plasminogen activator was tested in an embolic stroke model. The carotid territory was embolized in 103 rats with fibrin-rich clots formed and washed in polyethylene tubes. Hemispheric cerebral blood flow before and after embolization was measured by the intra arterial 133Xe injection method. At five delay times, 15–240 min after embolization, 69 animals were treated with tissue plasminogen activator, 20 mg/kg, and 34 animals with saline. Carotid angiography displayed the grade of occlusion of the cerebral arterial supply before and after treatment. Brains were fixed after 2 days, evaluated neuropathologically, and infarct volume measured. Cerebral blood flow was reduced by 56–71% after embolization. Reperfusion induced by thrombolytic therapy was demonstrated by comparing the posttreatment angiography of the pooled five treatment groups to control animals. Thrombolytic therapy significantly reduced the infarct volume and improved the prekill clinical score by up to 2 h of treatment delay, and treatment might have been beneficial even after 4 h delay. Prolonging the delay of treatment increased the infarct volume ( p < 0.001, Jonckheere–Terpstra test). Only a few hemorrhagic complications were observed. Thus, thrombolytic therapy in embolic stroke induced recanalization. The effect on clinical outcome and infarct volume was dependent on delay time.
Prolonged Expression of hsp70 mRNA following Transient Focal Cerebral Ischemia in Transgenic Mice Overexpressing CuZn-Superoxide Dismutase
Authors: Kamii Hideyuki , Kinouchi Hiroyuki , Sharp Frank R. , Koistinaho Jari , Epstein Charles J. , Chan Pak H.
Published: April 2011

The distribution of heat shock protein hsp70 mRNA after 10 min of middle cerebral artery (MCA) occlusion was investigated through in situ hybridization in transgenic (Tg) mice overexpressing CuZn-superoxide dismutase (CuZn-SOD) and in control nontransgenic (nTg) littermates. In the ischemic cortex of nTg mice, hsp70 mRNA was detected 1 h after reperfusion and was observed for up to 6 h. In Tg mice, however, it was still detectable within the cortex even at 24 h. In the caudate putamen, hsp70 mRNA appeared at 1 h and was present for up to 6 h in both nTg and Tg mice. Although hsp70 mRNA was detected in the thalamus only at 1 h in nTg mice, it was observed for up to 6 h in Tg mice. Similarly, hsp70 mRNA was detected in the hippocampus of nTg mice only at 1 h, whereas it was detected in Tg mice at 1 h and continued up to 24 h, with high intensity in the CA1 subfield. Despite the significant amounts of hsp70 mRNA in both Tg and nTg mice following ischemia, there was no observable neuronal necrosis (as assessed using hematoxylin and eosin staining) for up to 7 days. Cortical cerebral blood flow (CBF), measured by laser-Doppler flowmetry, did not differ between nTg and Tg mice during ischemia and reperfusion, despite exhibiting hyperemia following hypoperfusion. These results suggest that oxidative stress affects the expression of hsp70 following temporary local ischemia. An alteration in oxidation stress, which resulted from reduced levels of superoxide radicals in the presence of the CuZn-SOD transgenes, may permit the prolonged expression of hsp70. This prolonged expression of hsp70 mRNA in cortex cannot be accounted for by changes of CBF in Tg mice during ischemia and reperfusion.
Cerebral Blood Flow Autoregulation in Acute Intracranial Hypertension
Authors: Hauerberg John , Juhler Marianne
Published: April 2011

The present series of experiments was carried out to investigate CBF autoregulation during fixed levels of acute increased intracranial pressure (ICP). Three groups of six rats each, one with normal ICP (8 mm Hg), one with moderately increased ICP (30 mm Hg), and one with severely increased ICP (50 mm Hg), were investigated. ICP was maintained by continuous infusion of lactated Ringer solution into the cisterna magna. Cerebral perfusion pressure (CPP), calculated as mean arterial blood pressure – ICP, was increased by intravenously infused norepinephrine and decreased by controlled bleeding. In all groups the corresponding autoregulation curve included a plateau where CBF was independent of changes in CPP, demonstrating intact autoregulation. However, a significant shift of the lower limit of autoregulation (LL) toward lower CPP levels during severe intracranial hypertension was observed (p < 0.006). In the controls the LL was found at CPP = 73 ±6 mm Hg, in moderately increased ICP the LL was 59 ± 4 mm Hg, and in severely increased ICP the LL was 51 ±4 mm Hg. These results indicate that an acute elevation of ICP activates a reserve capacity of cerebral resistance vessels that dilate further below the normal physiological LL to maintain CBF at low levels of CPP.
Jean Brihaye Scholarship
Authors: Scholarship Jean Brihaye
Published: April 2011

The European Association of Neurosurgical Societies (EANS) will award the first Jean Brihaye Scholarship on the occasion of the 10th European Congress of Neurosurgery in Berlin, May 7–12, 1995. The scholarship amounts to ECU 12,000 (US$ 13,473.68) and will be awarded to a European neurosurgeon under the age of 45 (on May 12, 1995) for an unpublished scientific work in the field of neurosciences related to neurosurgery. The manuscript must have a maximum of 20 double-spaced typewritten pages. One original and eight photocopies must be sent before September 30, 1994 to: Prof. Dr. Mario Brock, President of the EANS, Universitätsklinikum Steglitz, Abteilung für Neurochirurgie, Hindenburgdamm 30, 12200 Berlin, Germany.
Closed Head Injury Triggers Early Production of TNFα and IL-6 by Brain Tissue
Authors: Shohami E. , Novikov M. , Bass R. , Yamin A. , Gallily R.
Published: April 2011

In a model of closed head injury (CHI) in the rat we have shown the activation of phospholipase A2 and the production of eicosanoids after injury: at 15 min, mainly 5-hydroxyeicosatetraenoic acid (5-HETE), and at 24 h, mainly prostaglandin E2. The present study was designed to test whether CHI can also trigger the production of cytokines in the brain. CHI was induced in ether-anesthesized rats by a weight-drop device falling over the exposed skull covering the left hemisphere, 1–2 mm lateral to the midline in the midcoronal plane. In the posttraumatic period (1–24 h), the rats were decapitated, cortical tissue from the injured zone of the contused and contralateral hemispheres was removed and sonicated, and cytokine activity was assessed. Whereas no tumor necrosis factor alpha (TNFα) activity was found in normal brain tissue, it was detectable in the contused hemisphere (∼72 ± 50 pg/mg protein) as early as 1 h post-CHI. TNFα levels increased at 2 h, peaked at 4 h, (-609 ± 540 pg/mg protein), and declined thereafter. At parallel intervals, only low levels of TNFα were detected in the contralateral hemisphere. In normal brain, interleukin-6 (IL-6) was nondetectable. Following CHI, high levels of IL-6 were present, although their accumulation lagged behind that of TNFα by 2–4 h, peaking at 8 h (62 ± 31 ng/mg protein). We suggest that the rapid production of TNFα and IL-6 following CHI is a local inflammatory response of brain tissue to primary insult.
Bilateral Simultaneous Assessment of Cerebral Flow Velocity during Mental Activity
Authors: Silvestrini Mauro , Cupini Letizia M. , Matteis Maria , Troisi Elio , Caltagirone Carlo
Published: April 2011

The purpose of this study was to assess the potential of transcranial Doppler (TCD) ultrasonography for detecting selective changes in cerebral blood flow velocity during mental activity. Mean flow velocity was continuously and simultaneously measured in the right and left middle cerebral arteries in 26 healthy right-handed young subjects at rest and during performance of verbal and visual-imaging mental tasks. These two mental tasks produced significantly different effects on the right and left sides: the verbal task produced a higher increase of flow velocity (mean absolute difference above baseline ± SD) with respect to the basal values in the left than in the right middle cerebral artery (5.56 ±3.8 cm/s vs 1.25 ± 3.1 cm/s); the visual-imaging task was accompanied by a higher increase in the right than in the left middle cerebral artery (3.92 ± 3.3 cm/s vs 1.52 ± 3.1 cm/s)—analysis of variance (ANOVA) three-fold interaction side of recording × task × condition, F = 25.67, p < .0001). Heart rate, blood pressure, and skin conductance showed comparable increases during performance of both mental tasks. Respiratory activity showed no modification during the mental activity with respect to the rest phase. These results demonstrate the possibility of delivering specific functional information via bilateral TCD and suggest wider utilization of this noninvasive technique in neuropsychological studies.
19F Magnetic Resonance Imaging of Cerebral Blood Flow with 0.4-cc Resolution
Authors: Pekar J. , Ligeti L. , Sinnwell T. , Moonen C. T. W. , Frank J. A. , McLaughlin A. C.
Published: April 2011

19F magnetic resonance imaging techniques were used to determine “wash-in” and “wash-out” curves of the inert, diffusible gas CHF3 from 0.4-cc voxels in the cat brain, and mass spectrometer gas detection was used to determine the CHF3 concentration in expired air. These two sets of data were used to calculate cerebral blood flow values in the 0.4-cc voxels, and the blood flow images were registered with high-resolution 1H magnetic resonance images. Data were collected both during the wash-in and wash-out phases of the experiment, but the two sets of data were analyzed separately to obtain independent estimates of the blood flow during the two phases, i.e., Qin and Qout. Repeated determinations of cerebral blood flow images were performed in individual animals, and the entire protocol was repeated on five different animals. The average values of Qin and Qout for a typical 0.4-cc voxel in the parietal cortex were 83 ml 100 g−1 min−1 and 72 ml 100 g−1 min−1, respectively. Monte Carlo calculations utilizing the noise in the 19F NMR signal from this voxel predict an average standard deviation for Qin and Qout of ± 10%. The average standard deviation for repeated measurements (in the same animal) of Qin and Qout in this voxel was ± 14%. We conclude that 19F magnetic resonance imaging approaches have the potential to image cerebral blood flow in humans.
Reduced Cerebral Blood Flow but Intact Reactivity to Hypercarbia and Hypoxia following Subarachnoid Hemorrhage in Rabbits
Authors: Diringer Michael N. , Kirsch Jeffrey R. , Traystman Richard J.
Published: April 2011

Subarachnoid hemorrhage (SAH) was produced in rabbits by four subarachnoid injections of blood (n = 7) or saline (n = 6); a control group (n = 6) had no injections. Basilar artery vasospasm was assessed by serial angiograms. Resting CBF (microspheres) and CBF reactivity to hypercapnia (65 and 85 mm Hg) and hypoxia (fractions of inspired oxygen of 0.15 and 0.10) were determined. Basilar artery vasospasm was seen with SAH. Resting CBF was reduced by 31% (SAH 43 ± 12, saline 65 ± 17, control 60 ± 21 ml 100 g−1 min−1), and resting cerebrovascular resistance was increased (SAH 1.84 ± 0.30, saline 1.31 ± 0.49, control 1.39 ± 0.25 mm Hg ml−1 100 g−1 min−1) after SAH. CBF rose to a similar degree in all three groups in response to hypercarbia and hypoxia. We conclude that resting CBF is reduced in this model of SAH, but vascular reactivity remains intact.
Acetazolamide Reactivity on 123I-IMP Single Photon Emission Computed Tomography in Patients with Major Cerebral Artery Occlusive Disease: Correlation with Positron Emission Tomography Parameters
Authors: Hirano Teruyuki , Minematsu Kazuo , Hasegawa Yasuhiro , Tanaka Yutaka , Hayashida Kohei , Yamaguchi Takenori
Published: April 2011

Single photon emission computed tomography (SPECT) with acetazolamide challenge has increasingly been used for evaluating hemodynamic reserve in stroke patients. The accuracy of this test, however, has not been validated with positron emission tomography (PET). In 14 patients who had occlusive disease of the internal carotid artery or the trunk of the middle cerebral artery (MCA) with minimal or no infarction on computed tomography (CT) and magnetic resonance imaging (MRI), we compared acetazolamide reactivity on SPECT with N-isopropyl- p-[123I]-iodoamphetamine to hemodynamic parameters determined with gas inhalation labeled 15O steady-state PET studies. The asymmetry index (AI)—i.e., the percentage of the activity rate of the ischemic MCA territory versus the contralateral one, was determined by SPECT. Acetazolamide reactivity expressed as ΔAI, or change in AI after acetazolamide challenge, was significantly lower in seven patients than −8.4%, the lower limit of the 95% confidence interval for the normal reactivity. Values of ipsilateral CBF, cerebral blood volume (CBV)/CBF, and oxygen extraction fraction (OEF) and contralateral OEF were significantly different between patients with normal and reduced acetazolamide reactivity. Values of AAI were correlated with OEF ( r = −0.87; p < 0.001) and CBV/CBF ( r = −0.56; p < 0.05). All patients with OEF >0.52, the mean + 2 SD calculated from five normal volunteers, also had reduced acetazolamide reactivity, while the patients with normal OEF values had normal reactivity. The present study has demonstrated that SPECT studies with an acetazolamide challenge can detect the Stage II hemodynamic failure.
Photic Stimulation Study of Changing the Arterial Partial Pressure Level of Carbon Dioxide
Authors: Shimosegawa Eku , Kanno Iwao , Hatazawa Jun , Fujita Hideaki , Iida Hidehiro , Miura Shuichi , Murakami Matsutarou , Inugami Atsushi , Ogawa Toshihide , Itoh Hiroshi , Okudera Toshio , Uemura Kazuo
Published: April 2011

To investigate the effect of the level of baseline cerebral blood flow (CBF) on local CBF augmentation by activation, we have used positron emission tomography to measure regional CBF (rCBF) in 12 normal volunteers with and without photic stimulation during hypocapnia, normocapnia, and hypercapnia. The increase in rCBF in the primary visual cortex by photic stimulation was 10.8 ± 3.1, 18.6 ± 9.3, and 19.5 ± 6.1 ml 100 ml−1 min−1 in hypo-, normo-, and hypercapnia, respectively. The increase was significantly smaller in hypocapnia than in normocapnia ( p < 0.005). The fractional CBF increase caused by the photic stimulation was the same in all breathing conditions. This result indicates that the magnitude of the CBF increase induced by neuronal activity correlates proportionally with the level of baseline CBF.
Improved Therapeutic Window for Treatment of Histotoxic Hypoxia with a Free Radical Spin Trap
Authors: Schulz Jörg B. , Matthews Russell T. , Jenkins Bruce G. , Brar Preetinder , Beal M. Flint
Published: April 2011

The therapeutic time window for N-methyl-d-aspartate (NMDA) antagonists, non-NMDA antagonists, and glutamate release inhibitors in focal models of ischemia appears to be about 1–2 h. In contrast, a free radical spin trap was found to have an improved therapeutic window. We compared the therapeutic time windows of the NMDA antagonist dizolcilpine maleate (MK-801), the glutamate release inhibitor lamotrigine, and the free radical spin trap n-tert-butyl-α-(2-sulfophenyl)-nitrone (S-PBN) against striatal lesions produced by the mitochondrial toxin malonate, which produces histotoxic hypoxia. Lamotrigine exerted neuroprotective effects when administered at 1 h before malonate injections. MK-801 protected at 1 h before and 1 h after malonate injections, whereas S-PBN showed efficacy when administered up to 6 h after malonate injections. Striatal injections of malonate produced a rapid increase in lactate production and early changes in diffusion-weighted imaging as assessed by magnetic resonance imaging. Therefore, the time course to evolve a lesion in our model of histotoxic hypoxia is comparable with that of other models of focal ischemia. These findings provide direct evidence that a free radical spin trap has an improved therapeutic window compared to an NMDA antagonist and a glutamate release inhibitor. This could be a therapeutic advantage in the treatment of clinical stroke patients.
Time-Related Neuronal Changes following Middle Cerebral Artery Occlusion: Implications for Therapeutic Intervention and the Role of Calpain
Authors: Bartus Raymond T. , Dean Reginald L. , Cavanaugh Kathy , Eveleth David , Carriero Debra L. , Lynch Gary
Published: April 2011

Changes in neocortex and striatum were characterized over time following focal ischemia to the brain. Rats were subjected to permanent middle cerebral artery occlusion (MCA-O) and sacrificed 1, 3, 6, 12, or 24 h later. The affected tissue was processed for tetrazolium chloride (TTC) and cresyl violet staining, as well as for Western blots to detect calpain-induced spectrin proteolysis. Significant changes in cell size and spectrin breakdown occurred within the first hour of occlusion, with further, dramatic changes in these two early markers continuing over time. Initial evidence of cell loss was noted at 1 h postocclusion in the striatum and at 3 h in the neocortex. However, even in the center of the most affected portion of the neocortex, the majority of cells appeared to be intact through 6 h. By this time, a significant TTC-defined infarct also emerged. These quantitative data indicate that calpain-induced proteolysis occurs very soon after the ischemic insult, is correlated with earliest changes in cell hypotrophy, and precedes or occurs in tandem with evidence of significant cell loss. They also demonstrate that, while some cell loss occurs earlier than previously believed, the majority of cells remains morphologically intact well beyond what is typically thought to be the window of opportunity for intervention. The results thus raise the question of how long after the ischemic event pharmaceutic intervention might be employed to salvage substantial numbers of neurons.
Hypoglycemia-Elicited Immediate Early Gene Expression in Neurons and Glia of the Hippocampus: Novel Patterns of FOS, JUN, and KROX Expression following Excitotoxic Injury
Authors: Gass Peter , Katsura Ken-Ichiro , Zuschratter Werner , Siesjö Bo , Kiessling Marika
Published: April 2011

In the hippocampus there is a graded vulnerability of neuronal subpopulations to hypoglycemia-induced degeneration, most likely due to excitotoxic activation of glutamate receptors. The present study was conducted to investigate whether the induction of transcription factors of the immediate early gene (IEG) family after hypoglycemia reflects these different grades of neuronal vulnerability. We studied the expression profile of seven IEG-coded proteins in the rat hippocampus following severe insulin-induced hypoglycemia with 30 min of EEG isoelectricity and various survival periods for up to 42 h after glucose replenishment. Immunocytochemistry was performed on vibratome sections with specific polyclonal antisera directed against c-FOS, FOS B, c-JUN, JUN B, JUN D, KROX-24, and KROX-20. To unequivocally define the type of glial cells showing IEG induction, we investigated coexpression of c-FOS and glial marker proteins (glial fibrillary acid protein [GFAP], OX-42) by confocal laser scanning microscopy. Up to 3 h after glucose replenishment, differential temporospatial induction of IEG-coded transcription factors of the FOS, JUN and KROX families were observed in moderately injured neuronal subpopulations, including the majority of dentate granule cells and CA3 neurons. At later time points, however, a delayed and persistent c-JUN expression was found in severely, but reversibly, injured CA1 neurons and in neurons in the immediate vicinity of irreversibly damaged neurons in the crest of the dentate gyrus. Similar to the results with experimental models of central and peripheral axotomy, selective c-JUN induction in these neurons may represent an initial event in the regeneration process of sublethally injured neurons. In contrast to other models of excitotoxic injury such as ischemia and epilepsy, marked glial c-FOS expression was restricted to astrocytes, as assessed by confocal laser scanning microscopy.
Induced Response to Hypercapnia in the Two-Compartment Total Cerebral Blood Volume: Influence on Brain Vascular Reserve and Flow Efficiency
Authors: Keyeux André , Ochrymowicz-Bemelmans Danielle , Charlier André A.
Published: April 2011

This study was undertaken to investigate the mechanisms of CBF increase as induced by hypercapnia. It was achieved in anesthetized rats by determining total cerebral blood volume (TCBV), parenchymal blood (CBV), plasma (CPV), erythrocyte (CEV) volumes and cerebral hematocrit (CHct) as well as CBF at about 40, 60, and 80 mm Hg Paco2. TCBV was measured by a noninvasive blood dilution method using [99mTc]pertechnetate. CBV, CPV, and CEV were measured on isolated brain by 125I-serum albumin and 51Cr-erythrocytes. CBF was measured by both [131I/14C]iodoantipyrine and 57Comicrosphere extractions. The extraparenchymal blood volume (ECBV) was evaluated by subtracting CBV from TCBV. Under normocapnia, ECBV was 2.8 times larger than CBV. Under moderate hypercapnia; ECBV increased by 44%, CBV was not modified, and CBF increased by 52%. These results demonstrate that the main site of vasodilation is located in the extraparenchymal vasculature, which thus acts as a vascular reserve. By contrast, under severe hypercapnia, ECBV remained unchanged, whereas CBV then increased by 17%; CBF simultaneously showed an additional augmentation of either 52 or 309% when diffusible tracer or microspheres were used. This important increase in CBF cannot be explained either by capillary recruitment of closed capillaries or by active diameter lengthening of already open capillaries. The concomitant and great increase in capillary blood velocity was also shown to reduce cerebral flow efficiency, a situation consistent with a “luxury perfusion.”
Simultaneous Measurements of Pial Arteriolar Diameter and Laser-Doppler Flow during Somatosensory Stimulation
Authors: Ngai Al C. , Meno Joseph R. , Winn H. Richard
Published: April 2011

We simultaneously measured pial arteriolar diameter and changes in cortical blood flow during activation of the somatosensory cortex by sciatic nerve stimulation. The pial vasculature was visualized with a closed-cranial window technique in chloralose-anesthetized rats ( n = 13). Local blood flow was monitored with laser-Doppler flowmetry. During stimulation of the sciatic nerve (0.2 V, 5 Hz, 20 s), vascular diameter and laser-Doppler flow consistently displayed similar response profiles. With 0.5-ms stimulation pulses, the responses showed an initial peak followed by a smaller but sustained plateau dilation. In contrast, 5-ms pulses evoked a monotonically rising response. Our results support the concept that pial arteriolar diameter changes reflect cortical blood flow responses during somatosensory stimulation.
Role of the Cerebellar Fastigial Nucleus in the Physiological Regulation of Cerebral Blood Flow
Authors: Takahashi Shinichi , Crane Alison M. , Jehle Jane , Cook Michelle , Kennedy Charles , Sokoloff Louis
Published: April 2011

Local cerebral blood flow (lCBF) was measured with [14C]iodoantipyrine in conscious, unrestrained rats during electrical stimulation of the fastigial nucleus (FN). Electrode position in the FN was determined by blood pressure (MABP) responses to stimulation under anesthesia. In nine rats in which MABP responses had been variable under anesthesia, bipolar stimulation (50 Hz, 0.5 ms, 1 s on/1 s off) with currents of 30–100 μA after recovery from anesthesia produced stereotypic behavior but little effect on MABP and lCBF. In seven other conscious rats currents could be raised to 75–200 μA without inducing seizures, resulting in sustained MABP elevations during the lCBF measurement and significantly increased lCBF in the sensory-motor (+ 45%), parietal (+ 31%), and frontal cortices (+ 56%) and the caudate-putamen (+ 27%) above control values ( n = 9). Glucose utilization, measured with [14C]deoxyglucose, in rats similarly stimulated was significantly increased in six structures, including some of the above, indicating increases in lCBF due to metabolic activation. Unilateral or bilateral electrolytic lesions of the FN, placed 6–7 days before lCBF measurement, had negligible effects on resting lCBF and on autoregulation in conscious rats. These results fail to support a specific role for the FN in physiological regulation of cerebral blood flow in unanesthetized rats.
Spreading Waves of a Reduced Diffusion Coefficient of Water in Normal and Ischemic Rat Brain
Authors: Hasegawa Yasuhiro , Latour Lawrence L. , Formato James E. , Sotak Christopher H. , Fisher Marc
Published: April 2011

Using echo planar diffusion-weighted magnetic resonance imaging, we measured three-dimensional changes in the apparent diffusion coefficient (ADC) of water in eight contiguous coronal slices, encompassing the entire rat brain, before and after local cortical stimulation. We applied chemical (potassium chloride application; n = 6) and mechanical (needle stab; n = 4) stimulations to the right posterior parietal rat cortex. In all animals in which potassium chloride or the needle stab was applied, a region of decreased ADC values to a mean of 0.45 ± 0.03 × 10−5cm2/s occurred. These reduced ADC levels appeared in the posterior parietal cortex within 1 min after cortical stimulation and the change recovered within 1 min. Then a ripple-like movement of similar changes developed across the unilateral cortex. This change was localized to the cortex and no significant ADC changes occurred in subcortical structures. The propagating speed of this movement was 3.4 ± 0.5 mm/min. These findings are compatible with spreading depression as observed electrophysiologically. Similar ADC changes occurred in areas distinct from the ischemic lesion in 3 of 12 animals subjected to focal cerebral ischemia. This magnetic resonance method could detect spreading ADC decline if it occurred in human diseases including brain ischemia.
The Neuroprotective Effect of the Glycine Site Antagonist 3R-(+)-cis-4-Methyl-HA966 (L-687,414) in a Rat Model of Focal Ischaemia
Authors: Gill R. , Hargreaves R. J. , Kemp J. A.
Published: April 2011

3 R-(+)- cis-4-Methyl-HA966 (L-687,414) is a novel and selective, low intrinsic activity, partial agonist at the glycine site of the N-methyl-d-aspartate (NMDA) receptor. Thus, while it acts primarily to block NMDA receptor function in the presence of glycine, it fails to produce a complete block of NMDA receptor activation. In this study, we have investigated its neuroprotective effects in a rat model of focal ischaemia, involving permanent occlusion of the left middle cerebral artery. L-687,414 was administered as a bolus dose of 17.6 mg/kg i.v. straight after the occlusion or as a bolus dose + infusion for 4 h. The doses of L-687,414 used for the infusion studies were 7 mg/kg i.v. +7 mg/kg/h, 14 mg/kg + 14 mg/kg/h, or 30 mg/kg + 30 mg/kg/h. The 17.6-mg/kg dose gave an estimated peak plasma level of 24 μg/ml, which decayed with a tI/2 of 56 min. The three infusion dosing regimens gave mean plasma levels over the 4 h of 11, 25, and 61 μg/ml plasma, respectively. The 17.6-mg/kg dose of L-687,414 gave no significant protection against the volume of hemispheric, cortical, or caudate damage when compared with the control group of animals. The lowest infusion dosing regimen of L-687,414 which gave a plasma level of 11 μg/ml over the 4 h was also ineffective against the volume of infarction measured in the different brain regions. The middle dose of L-687,414 (25 μg/ml) gave a highly significant reduction in the volume of ischaemic brain damage for the hemisphere and cerebral cortex, volumes of ischaemic tissue being reduced by 34 and 41% compared with saline-treated animals, respectively. The highest plasma concentration of L-687,414 (61 μg/ml) resulted in a 18% reduction in the volume of hemispheric damage and a 21% reduction in the volume of cortical damage, which were significant. The reduced protection afforded by the highest dose of L-687,414 may be due to the slight hypotensive (MABP decreased by 13–16 mm Hg) effect produced by this dose. There was no protection seen against the volume of damage in the caudate nucleus for any of the doses of L-687,414 tested. Thus, L-687,414 was effective in producing neuroprotection in this model of ischaemia at doses that do not affect MABP or have any other of the adverse effects associated with neuroprotective doses of NMDA receptor ion channel blockers such as MK-801.
Ischemia-Induced Release of Amino Acids in the Hippocampus of Aged Hypertensive Rats
Authors: Ooboshi Hiroaki , Sadoshima Seizo , Yao Hiroshi , Ibayashi Setsuro , Matsumoto Takashi , Uchimura Hideyuki , Fujishima Masatoshi
Published: April 2011

We have recently demonstrated the age-related vulnerability of hippocampal neurons to 20-min forebrain ischemia in spontaneously hypertensive rats (SHR). In the present study, we investigated the effect of aging on the release of amino acids in the hippocampus during transient cerebral ischemia for 20 min. Concentrations of extracellular amino acids and cerebral blood flow in the CA1 subfield were examined by an in vivo brain dialysis technique and a hydrogen clearance method, respectively, in adult (5–7 month) and aged (19–23 month) female SHR. During cerebral ischemia by bilateral carotid artery occlusion, cerebral blood flow to the hippocampus decreased to 20% of the resting values in both groups. After recirculation, both groups showed delayed hypoperfusion which was more prominent in the aged SHR. In the adult rats, concentrations of both aspartate and glutamate increased to ∼8-fold of the resting values during ischemia. The elevation of these excitatory amino acids in the adult SHR was not significantly different from that in the aged rats. In contrast, the concentration of taurine increased 26-fold in the adult SHR but only 16-fold in the aged rats. Changes in other amimo acids were not different between the two groups. These results indicate that an imbalance of excitatory and inhibitory amino acids, e.g., smaller release of taurine, during ischemia may, at least in part, contribute to the age-related vulnerability of hippocampal neurons to transient cerebral ischemia in SHR.
Concomitant EEG, Lactate, and Phosphorus Changes by 1H and 31P NMR Spectroscopy during Repeated Brief Cerebral Ischemia
Authors: Conger Karl A. , Halsey James H. , Luo Kang-Li , Tan Min-Jie , Pohost Gerald M. , Hetherington Hoby P.
Published: April 2011

Pilots of high-performance aircraft are subject to transient loss of consciousness due to cerebral ischemia resulting from sudden high gravitational stress. To assess the effects of gravitational stress-induced blackout on cerebral metabolism and electrical function, we developed an animal model in which global cerebral ischemia is produced repeatedly at short intervals. Rats were prepared by ligation of subclavian and external carotid arteries and the right carotid artery was cannulated bidirectionally to measure circle of Willis and systemic pressures. Ischemia was induced by inflation of an occluder about the left carotid artery. Interleaved 31P and 1H NMR spectra were acquired on a 4.7-T Biospec system simultaneously with EEG recordings. We report results from 20 experiments of 30-min duration in which rats were subject to 30 1-min ischemia:reflow cycles of 10I:50R, 20I:40R, 30I:30R, and 40I:20R [numbers are seconds of ischemia (I) and reflow (R) during each 1-min cycle]. During ischemia the graded delivery of the ischemic insult permitted direct correlations between 2- to 5- and 7- to 20-Hz EEG activity and progressive changes in pH, lactate, ATP, phosphocreatine (PCr) and Pi. The best correlations were found between EEG activity and pH and PCr; correlation coefficients ranged from 0.93 to 0.95. A loss of EEG activity was observed without significant sustained energy loss in all but the most severe cycle.
Induction of CL100 Protein Tyrosine Phosphatase following Transient Forebrain Ischemia in the Rat Brain
Authors: Takano Seiichirou , Fukuyama Hidenao , Fukumoto Manabu , Hirashimizu Kazunori , Higuchi Toshihiro , Takenawa Jun , Nakayama Hiroki , Kimura Jun , Fujita Jun
Published: April 2011

Protein tyrosine phosphorylation is thought to play an important role in the regulation of neural function. To elucidate the role that protein tyrosine phosphatases (PTPs) may play in the postischemic brain, PTPs expressed in regions of the rat brain vulnerable to transient forebrain ischemia were examined. With the reverse-transcriptase polymerase chain reaction using degenerate primers, three PTPs, STEP, PTPS, and SH-PTP2, were identified. They were expressed in the hippocampus 12 h after transient ischemia for 20 min. During the reperfusion period, the mRNA levels of these PTPs were not different from those in sham-operated rats. In contrast, a fourfold increase in the mRNA level of CL100 (3CH134), a PTP that is inducible by oxidative stress, was detected by Northern blotting in the hippocampus and cerebral cortex 1 h after the onset of reperfusion. In situ hybridization histochemistry showed a slight increase in the level of CL100 mRNA in neuronal cells in the hippocampus and cortex of postischemic rats compared to control rats. These findings suggest that PTPs play a role in the normal function of the hippocampus and cerebral cortex and demonstrate that ischemia induced CL100 expression.
Neuroprotection by Peptide Growth Factors against Anoxia and Nitric Oxide Toxicity Requires Modulation of Protein Kinase C
Authors: Maiese Kenneth , Boccone Lauraine
Published: April 2011

Basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) are neuroprotective during anoxia and nitric oxide (NO) toxicity. Signal transduction systems that modulate protein kinase C (PKC) also can modulate the toxic effects of anoxia and NO. We therefore examined whether PKC was involved in the protective effects of bFGF and EGF during anoxia and NO toxicity. Down-regulation or inhibition of PKC activity before anoxia or NO exposure prevented hippocampal neuronal degeneration. Yet, this protective effect of inhibition of PKC activity was not present with the coadministration of growth factors. Combined inhibition of PKC activity and application of bFGF or EGF lessened the protective mechanisms of the growth factors. In addition, the protective ability of the growth factors was lost during anoxia and NO exposure with the activation of PKC, suggesting that at least a minimal degree of PKC activation is necessary for growth factor protection. Although modulation of PKC activity may be a necessary prerequisite for protection against anoxia and NO toxicity by bFGF and EGF, only inhibition of PKC activity, rather than application of the growth factors, was protective following exposure to NO. These results suggest that the mechanism of protection by bFGF and EGF during anoxia and NO toxicity appears initially to be dependent on a minimum degree of PKC activation, but that other signal transduction pathways independent of PKC also may mediate protection by peptide growth factors.
A Synaptic Vesicle-Associated Protein (SVP-38) as an Early Indicator of Delayed Neuronal Death
Authors: Miyazawa Takahito , Sato Kiyoshi , Obata Kunihiko
Published: April 2011

Sixteen gerbils were subjected to 5 min of forebrain ischemia. Their brains were processed for immunohistochemical staining using monoclonal antibodies against a synaptic vesicle-associated protein 38 (SVP-38) and microtubule-associated protein 2 (MAP2) after recirculation times of 10 min, and 1, 4, and 7 days. After 10 min recirculation, SVP-38 immunoreactive dots were observed only in the CA1 region of the hippocampus. After 1 day recirculation, SVP-38 immunostaining was diffuse and weak throughout the hippocampus, despite preservation of MAP2 immunoreactivity. After 4 and 7 days recirculation, SVP-38 immunoreactivity had been restored in the whole hippocampus, despite the complete loss of MAP2 immunoreactivity due to delayed neuronal death. Our results demonstrate an immediate and significant change in the immunoreactivity of a synaptic vesicle–associated protein at the beginning of the process of delayed neuronal death. Thus, changes in the immunoreactivity of synaptic vesicle-associated proteins such as SVP-38 appear to be one of the earliest indicators of the onset of neuronal death.
Regional Induction of c-Fos and Heat Shock Protein-72 mRNA following Fluid-Percussion Brain Injury in the Rat
Authors: Raghupathi Ramesh , Welsh Frank A. , Lowenstein Daniel H. , Gennarelli Thomas A. , McIntosh Tracy K.
Published: April 2011

To evaluate the cellular response to traumatic brain injury, the expression of mRNA for c- fos and the 72-kDa heat shock protein (hsp72) was determined using in situ hybridization following lateral fluid-percussion injury (2.2–2.4 atm) in rat brain. At 2 h after injury, induction of c- fos mRNA was observed throughout the cortex ipsilateral to the site of injury, while increased expression of hsp72 mRNA was restricted to regions of the cortex surrounding the contusion area. An increase in c- fos mRNA, but not hsp72 mRNA, was observed bilaterally in the CA3 subfield of the hippocampus and the granule cells of the dentate gyrus and in the thalamus ipsilateral to the impact site. By 6 h, increased expression of c- fos mRNA was observed only in the corpus callosum on the impact side; hsp72 mRNA persisted in the deep cortical layers and upper layers of the subcortical white matter below the site of maximal injury. By 24 h, both c- fos and hsp72 mRNA had returned to control levels in all regions of the brain. These results demonstrate that lateral fluid– percussion brain injury triggers regionally and temporally specific expression of c- fos and hsp72 mRNA, which may be suggestive of differential neurochemical alterations in neurons and glia following experimental brain injury.
Analysis of PET Neurofunctional Mapping Studies
Authors: Votaw John R. , Li Hengli H.
Published: April 2011

In this work, we present a method for analyzing positron emission tomography (PET) functional mapping experiments. The method is useful for identifying statistically significant differences between two PET data sets. First, uniform-variance Z-images are created and then the statistical uncertainty in region-of-interest values are calculated using a previously published method. The Z-images are calculated from the emission sinograms only
Differential Effects of Alcohols on Intracerebral Arterioles. Ethanol Alone Causes Vasoconstriction
Authors: Gordon Ellen L. , Nguyen T.-S. , Ngai Al C. , Winn H. Richard
Published: April 2011

We compared the effect of the acute application of ethanol, methanol, 1-propanol, 1-butanol, urea, and mannitol (1–100 m M) on the basal tone of isolated–cannulated rat intracerebral arterioles to determine if the response of these arterioles to ethanol could be attributed to alteration of membrane fluidity or changes in osmolality. These arterioles spontaneously developed tone to 62.0 ± 8.4% of passive diameter (44.2 ±11.9 vs. 70.9 ± 14.7 μm). Ethanol caused a dose-dependent reduction in arteriolar diameter starting at 3 m M (p = 0.03), reaching a diameter of 81.4 ± 3.0% of basal tone at 100 m M. In comparison, all other agents tested caused the arterioles to dilate, with the exception of 1-propanol, which produced inconsistent vessel responses. At 100 m M concentration, methanol, 1-butanol, urea, and mannitol dilated intracerebral arterioles by 116.1 ± 12.7, 151.5 ± 12.4, 131.1 ± 17.0, and 149.8 ± 6.6%, respectively. Thus, in a concentration range associated with acute intoxication, ethanol causes constriction of isolated intracerebral arterioles. The mechanism of action of ethanol cannot be accounted for solely based upon its physicochemical characteristics of osmolality or lipid solubility, but rather may reflect a more specific action on one or more cellular mechanisms responsible for determining basal intracerebral arteriolar tone. The characterization of the response of intracerebral arterioles to ethanol is important in view of epidemiologic links between ethanol consumption and cerebrovascular disease.
Basic Fibroblast Growth Factor Protects against Excitotoxicity and Chemical Hypoxia in Both Neonatal and Adult Rats
Authors: Kirschner Pamela B. , Henshaw Ross , Weise Jens , Trubetskoy Vladimir , Finklestein Seth , Schulz Jörg B. , Beal M. Flint
Published: April 2011

Basic fibroblast growth factor (bFGF) is a polypeptide growth factor that promotes neuronal survival. We recently found that systemic administration of bFGF protects against both excitotoxicity and hypoxia–ischemia in neonatal animals. In the present study, we examined whether systemically administered bFGF could prevent neuronal death induced by intrastriatal injection of N-methyl-d-aspartate (NMDA) or chemical hypoxia induced by intrastriatal injection of malonate in adult rats and 1-methyl-4-phenylpyridinium (MPP+) in neonatal rats. Systemic administration of bFGF (100 μg/kg) for three doses both before and after intrastriatal injection of either NMDA or malonate in adult rats produced a significant neuroprotective effect. In neonatal rats, bFGF produced dose-dependent significant neuroprotective effects against MPP+ neurotoxicity, with a maximal protection of ∼50% seen with either a single dose of bFGF of 300 μg/kg or three doses of 100 μg/kg. These results show that systemic administration of bFGF is effective in preventing neuronal injury under circumstances in which the blood–brain barrier may be compromised, raising the possibility that this strategy could be effective in stroke.
Glial Expression of the β-Amyloid Precursor Protein (APP) in Global Ischemia
Authors: Banati R. B. , Gehrmann J. , Wießner C. , Hossmann K.-A. , Kreutzberg G. W.
Published: April 2011

The β-amyloid precursor protein (APP) bears characteristics of an acute-phase protein and therefore is likely to be involved in the glial response to brain injury. In the brain, APP is rapidly synthesized by activated glial cells in response to comparatively mild neuronal lesions, e.g., a remote peripheral nerve injury. Perfusion deficits in the brain result largely in neuronal necrosis and are a common condition in elderly patients. This neuronal necrosis is accompanied by a pronounced reaction of astrocytes and microglia, which can also be observed in animal models. We have therefore studied in the rat, immunocytochemically, the induction of APP after 30 min of global ischemia caused by four-vessel occlusion. The postishemic brain injuries were examined at survival times from 12 h to 7 days. From day 3 onward, APP immunoreactivity was strongly induced in the CA1 and CA4 regions of the rat dorsal hippocampus as well as in the dorsolateral striatum. In these areas, the majority of APP-immunoreactive cells were reactive glial fibrillary acidic protein (GFAP)-positive astrocytes, as shown by double-immunofluorescence labeling for GFAP and APP. Additionally, small ramified cells, most likely activated microglia, expressed APP immunoreactivity. In contrast, in the parietal cortex, APP immunoreactivity occurred focally in clusters of activated microglia rather than in astrocytes, as demonstrated by double-immunofluorescence labeling for APP and the microglia-binding lectin Griffonia simplicifolia isolectin B4. In conclusion, following global ischemia, APP is induced in reactive glial cells with spatial differences in the distribution pattern of APP induction in astrocytes and microglia.