bluuebunny/crossref_metadata_2025 huggingface dataset:
Acute Focal Ischemia-Induced Alterations in MAP2 Immunostaining: Description of Temporal Changes and Utilization as a Marker for Volumetric Assessment of Acute Brain Injury
Authors: Dawson Deborah A. , Hallenbeck John M.
Published: November 2003

The utility of microtubule-associated protein 2 (MAP2) immunostaining as a marker of acute focal ischemic injury was investigated. Permanent middle cerebral artery occlusion (MCAO) elicited a rapid reduction in MAP2 immunostaining that was visible 1 h post-MCAO and that increased in intensity and area encompassed over time. The ischemic lesion borders were well defined by loss of MAP2 immunostaining, but alterations in staining within the lesion were more heterogeneous. Lesion volume increased significantly from 1 to 4 h post-MCAO (from 63.8 ± 10.8 to 111.3 ± 19.0 mm3, mean ± SD). Thus, MAP2 immunostaining is a sensitive, quantifiable indicator of acute brain injury following focal ischemia.
Overexpression of the Glucose Transporter Gene with a Herpes Simplex Viral Vector Protects Striatal Neurons against Stroke
Authors: Lawrence Matthew S. , Sun Guo Hua , Kunis David M. , Saydam Tippi C. , Dash Raj , Ho Dora Y. , Sapolsky Robert M. , Steinberg Gary K.
Published: November 2003

Herpes simplex virus vectors bearing a glucose transporter (GT) gene and a marker gene were found to protect neurons against a 1-h focal ischemic insult. Rats receiving the GT vector vα22βgalα4GT exhibited a 67.4 ± 35.3% survival of virally targeted neurons in the ischemic hemisphere compared with the contralateral control (n = 7), whereas rats receiving a control vector exhibited only 32.8 ± 17.9% survival (n = 9). This significant improvement in survival (105%, p = 0.022) suggests that energy failure is an important contributor to the neuropathology of ischemic damage in the striatum, and that it can be alleviated by gene transfer. This is the first demonstration of protection against ischemic cerebral injury by the direct transfer of GT genes to neurons.
Apoptosis and Necrosis after Reversible Focal Ischemia: An in Situ DNA Fragmentation Analysis
Authors: Charriaut-Marlangue C. , Margaill I. , Represa A. , Popovici T. , Plotkine M. , Ben-Ari Y.
Published: November 2003

Apoptosis is one of the two forms of cell death and occurs under a variety of physiological and pathological conditions. Cells undergoing apoptotic cell death reveal a characteristic sequence of cytological alterations including membrane blebbing and nuclear and cytoplasmic condensation. Early activation of an endonuclease has been previously demonstrated after a transient focal ischemia in the rat brain ( Charriaut-Marlangue C, Margaill I, Plotkine M, Ben-Ari Y (1995) Early endonuclease activation following reversible focal ischemia. J Cereb Blood Flow Metab 15:385–388). We now show that a significant number of striatal and cortical neurons exhibited chromatin condensation, nucleus segmentation, and apoptotic bodies increasing with recirculation time, as demonstrated by in situ labeling of DNA breaks in cryostat sections. Apoptotic nuclei were also detected in the horizontal limb diagonal band, accumbens nucleus and islands of Calleja. Several necrotic neurons, in which random DNA fragmentation occurs, were also shown at 6 h recirculation, in the ischemic core. Further investigation with hematoxylin/eosin staining revealed that apoptotic nuclei were present in cells with a large and swelled cytoplasm and in cells with an apparently well-preserved cytoplasm. These two types of cell death were reminiscent of those described in developmental cell death. Our data suggested that apoptosis may contribute to the expansion of the ischemic lesion.
Very Delayed Infarction after Mild Focal Cerebral Ischemia: A Role for Apoptosis?
Authors: Du Cheng , Hu Rong , Csernansky Cynthia A. , Hsu Chung Y. , Choi Dennis W.
Published: November 2003

The temporal evolution of cerebral infarction was examined in rats subjected to transient occlusion of both common carotid arteries and the right middle cerebral artery. After severe (90-min) ischemia, substantial right-sided cortical infarction was evident within 6 h and fully developed after 1 day. After mild (30-min) ischemia, no cortical infarction was present after 1 day. However, infarction developed after 3 days; by 2 weeks, infarction volume was as large as that induced by 90-min ischemia. These data suggest that infarction after mild focal ischemia can develop in a surprisingly delayed fashion. Some evidence of neuronal apoptosis was present after severe ischemia, but only to a limited degree. However, 3 days after mild ischemia, neurons bordering the maturing infarction exhibited prominent TUNEL staining, and DNA prepared from the periinfarct area of ischemic cortex showed internucleosomal fragmentation. Furthermore, pretreatment with 1 mg/kg cycloheximide markedly reduced infarction volume 2 weeks after mild ischemia. These data raise the possibility that apoptosis, dependent on active protein synthesis, contributes to the delayed infarction observed in rats subjected to mild transient focal cerebral ischemia.
MR Detection of Cortical Spreading Depression Immediately after Focal Ischemia in the Rat
Authors: Röther Joachim , de Crespigny Alexander J. , D'Arceuil Helen , Moseley Michael E.
Published: November 2003

The suture model for middle cerebral artery occlusion (MCAO) was used to induce acute ischemia in rats remotely within a magnetic resonance (MRI) scanner. Serial MR diffusion weighted imaging (DWI) was performed during remote MCAO using an echo planar imaging technique. MR perfusion imaging was performed before and after occlusion using the bolus tracking technique. Transient apparent diffusion coefficient (ADC) changes were detected in six of seven rats as early as 2.7 ± 1.5 min post MCAO. ADC values declined transiently to 70.1 ± 6.0% of control and recovered to 95.5 ± 6.8% of control within 3.3 ± 2.9 min. These ADC changes propagated bidirectionally away from the ischemic core with a speed of 3.0 ± 1.1 mm/min. Transient ADC decreases only occurred in ischemic areas characterized by moderately decreased tissue perfusion. Propagation toward cortical regions with severe tissue perfusion deficits was not detected. DWI can detect the earliest dynamic, reversible ADC changes in the ischemic tissue. The speed of propagation of the decreasing ADC wave, the waveform characteristics, and the occurrence in moderately perturbated tissue are compatible with cortical spreading depression.
Role of Nitric Oxide in the Elevation of Cerebral Blood Flow Induced by Acetylcholine and Anoxia in the Turtle
Authors: Hylland Patrick , Nilsson Göran E. , Lutz Peter L.
Published: November 2003

Nitric oxide (NO)-dependent regulation of brain blood flow has hitherto not been studied in reptiles. By observing the brain surface (telencephalon) of the freshwater turtle (Trachemys scripta) with epiillumination microscopy, we show that topical application of acetylcholine (ACh) induces an increase in CBF velocity that can be completely blocked by the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME). The effect of L-NAME was reversed by L-arginine. Also, sodium nitroprusside (SNP), which decomposes to liberate NO, caused an increase in CBF velocity. By contrast, L-NAME could not block the increase in blood flow velocity caused by anoxia. Interestingly, superfusing the brain with ACh or SNP during anoxia had no effect on the blood flow velocity. The results suggest that NO is an endogenous vasodilator in the turtle brain, mediating the effects of ACh during normoxia. By contrast, anoxia does not rely on NO as a vasodilator.
Impaired Calcium Regulation of Smooth Muscle during Chronic Vasospasm following Subarachnoid Hemorrhage
Authors: Kim Phyo , Yoshimoto Yuhei , Iino Masamitsu , Tomio Sasaki , Kirino Takaaki , Nonomura Yoshiaki
Published: November 2003

The intracellular calcium level was determined in the canine basilar artery to investigate whether Ca2+regulation of its smooth muscle is altered during chronic vasospasm following subarachnoid hemorrhage. A double-hemorrhage model was used. The occurrence of vasospasm was confirmed angiographically 7 days after initial hemorrhage. The intracellular calcium concentration ([Ca2+]i) of smooth muscle was measured using Fura-2. Fluorescence to excitation at 340 and 356 nm was monitored and the ratio R340/356 was used as the indicator of [Ca2+]i. When the extracellular calcium concentration ([Ca2+]e) was increased from pCa 8 to 2, [Ca2+]i also increased. In the spastic arteries, the [Ca2+]e − [Ca2+]i curve was elevated as compared with the normal arteries. Treatment with ionomycin elevated the curve in the normal group, but it had little effect in the spastic arteries. Values of [Ca2+]i, calculated in multiples of Kd, were greater in the spastic arteries. Diltiazem (10;−5 mol/L) partially suppressed the augmented [Ca2+]i signal in the spastic arteries, whereas it did not affect the curve in the control group. These results indicate that calcium regulation of smooth muscle is impaired after subarachnoid hemorrhage, which may contribute to the pathogenesis of chronic vasospasm.
Proteolytic Cascade Enzymes Increase in Focal Cerebral Ischemia in Rat
Authors: Rosenberg Gary A. , Navratil Milo , Barone Frank , Feuerstein Giora
Published: November 2003

Cerebral infarction initiates a cascade of molecular events, leading to proteolytic cell death. Matrix-degrading metalloproteinases (MMPs) are neutral proteases involved in extracellular matrix damage. Type IV collagenase is an MMP that increases cerebral capillary permeability after intracerebral injection and may be important along with plasminogen activators (PA) in secondary brain edema in stroke. Therefore, we measured MMPs and PAs in spontaneously hypertensive (SHR) or Wistar-Kyoto (WKY) rats with permanent middle cerebral artery occlusion (MCAO). Brain tissue was assayed for MMPs and PAs at 1, 3, 12, and 24 h and 5 days after occlusion, using substrate gel Polyacrylamide electrophoresis (zymography). SHR showed an increase in 92-kDa type IV collagenase (gelatinase B) in the infarcted hemisphere compared with the opposite side at 12 and 24 h ( p < 0.05). Gelatinase A remained the same in both infarcted and normal tissue until 5 days after injury, when it increased significantly ( p < 0.05). Urokinase-type PA was increased significantly at 12 and 24 h and 5 days, while tissue-type PA was decreased significantly at 1, 12, and 24 h in the ischemic compared with the nonischemic hemisphere. Gelatinase B was markedly increased in SHR at 12 and 24 h compared with WKY ( p < 0.05). Secondary vasogenic edema is maximal 1–2 days after a stroke, which is the time that gelatinase B was elevated. The time of appearance of gelatinase B suggests a role in secondary tissue damage and vasogenic edema, while gelatinase A may be involved in tissue repair.
The Metabolic Topography of Normal Aging
Authors: Moeller J. R. , Ishikawa T. , Dhawan V. , Spetsieris P. , Mandel F. , Alexander G. E. , Grady C. , Pietrini P. , Eidelberg D.
Published: November 2003

Normal aging is associated with the degeneration of specific neural systems. We used [18F]fluorode-oxyglucose (FDG)/positron emission tomography (PET) and a statistical model of regional covariation to explore the metabolic topography of this process. We calculated global and regional metabolic rates for glucose (GMR and rCMRglc) in two groups of normal subjects studied independently on different tomographs: Group 1—130 normal subjects (62 men and 68 women; range 21–90 years); Group 2—20 normal subjects (10 men and 10 women; range 24–78 years). In each of the two groups, the Scaled Subprofile Model (SSM) was applied to rCMRglc data to identify specific age-related profiles. The validity of these profiles as aging markers was assessed by correlating the associated subject scores with chronological age in both normal populations. SSM analysis disclosed two significant topographic profiles associated with aging. The first topographic profile, extracted in an analysis of group 1 normals, was characterized by relative frontal hypometabolism associated with covariate metabolic increases in the parietooccipital association areas, basal ganglia, mid-brain, and cerebellum. Subject scores for this profile correlated significantly with age in both normal groups ( R2 = 0.48 and 0.33, p < 0.0001 for groups 1 and 2, respectively). Because of clinical similarities between normal motoric aging and parkinsonism, we explored the possibility of shared elements in the metabolic topography of both processes. We performed a combined group SSM analysis of the 20 group 2 normals and 22 age-matched Parkinson's disease patients, and identified another aging-related topographic profile. This profile was characterized by relative basal ganglia hypermetabolism associated with covariate decreases in frontal premotor cortex. Subject scores for this profile also correlated significantly with age in both normal groups (group 1: R2 = 0.30, p < 0.00001; group 2: R2 = 0.59, p < 0.01). Healthy aging is associated with reproducible topographic covariation profiles associated with specific neural systems. FDG/PET may provide a useful metabolic marker of the normal agingprocess.
Stereotaxic Summation Analysis of Human Cerebral Benzodiazepine Binding Maps
Authors: Frey K. A. , Minoshima S. , Koeppe R. A. , Kilbourn M. R. , Berger K. L. , Kuhl D. E.
Published: November 2003

Summation analysis strategies are recognized throughout diverse scientific fields as powerful means of differentially enhancing experimental signals over random fluctuations (noise). Such techniques, applied to emission tomographic cerebral blood flow scans, reveal subtle alterations in neuronal activity during specific behavioral states. In the present work, we extend the principles of intersubject image summation analysis to the evaluation of emission tomographic ligand-binding studies. A general methodology is presented that may be applied to a wide variety of binding site determinations. The procedure consists of anatomic standardization of individual brains to a common stereotaxic orientation, followed by statistical analyses of group versus group or individual versus group differences. We develop and evaluate performance of our technique with the use of positron emission tomographic [11C]flumazenil scans from normal volunteers, depicting the regional cerebral distribution of benzodiazepine binding sites.
1H NMR Studies of Glucose Transport in the Human Brain
Authors: Gruetter Rolf , Novotny Edward J. , Boulware Susan D. , Rothman Douglas L. , Shulman Robert G.
Published: November 2003

The difference between 1H nuclear magnetic resonance (NMR) spectra obtained from the human brain during euglycemia and during hyperglycemia is depicted as well-resolved glucose peaks. The time course of these brain glucose changes during a rapid increase in plasma glucose was measured in four healthy subjects, aged 18–22 years, in five studies. Results demonstrated a significant lag in the rise of glucose with respect to plasma glucose. The fit of the integrated symmetric Michaelis–Menten model to the time course of relative glucose signals yielded an estimated plasma glucose concentration for half maximal transport, Kt, of 4.8 ± 2.4 m M (mean ± SD), a maximal transport rate, Tmax, of 0.80 ± 0.45 μmol g–1 min–1, and a cerebral metabolic glucose consumption rate (CMR)glc of 0.32 ± 0.16 μmol g“1 min”1. Assuming cerebral glucose concentration to be 1.0 μmol/g at euglycemia as measured by 13C NMR, the fit of the same model to the time course of brain glucose concentrations resulted in Kt = 3.9 ± 0.82 m M, Tmax = 1.16 ± 0.29 μmol g–1 min–1, and CMRglc = 0.35 ± 0.10 μmol g–1 min–1. In both cases, the resulting time course equaled that predicted from the determination of the steady-state glucose concentration by 13C NMR spectroscopy within the experimental scatter. The agreement between the two methods of determining transport kinetics suggests that glucose is distributed throughout the entire aqueous phase of the human brain, implying substantial intracellular concentration.
Flow Threshold for Reduction of Cyclic AMP Binding in the Hippocampus CA1 and other Brain Regions during Stroke Development in Gerbils
Authors: Tanaka Kortaro , Gomi Shintaro , Mihara Ban , Shirai Toshitaka , Nogawa Shigeru , Nozaki Hiroyuki , Nagata Eiichiro , Kondo Taro , Fukuuchi Yasuo
Published: November 2003

The flow threshold for alterations of the in vitro [3H]cyclic AMP (cAMP) binding, an indicator of the total amount of particulate cAMP-dependent protein kinase, was evaluated in the gerbil brain after 30 min, 2 h, and 6 h of unilateral common carotid artery occlusion, respectively. The autoradiographic method developed in our laboratory enabled us to measure the [3H]cAMP binding and local CBF in each region of the same brain. The ischemic flow thresholds for reduction of the cAMP binding in the hippocampus CA1 were 18, 34, and 49 ml 100 g–1 min–1 after 30-min, 2-h, and 6-h ischemia, respectively. These values were higher than those in other regions such as the hippocampus CA3 and temporal cerebral cortex in each duration of ischemia. These findings indicate that (a) the ischemic flow threshold for perturbation of the cAMP system may be higher in the hippocampus CA1 than in other brain regions, suggesting that the hippocampus CA1 could be especially vulnerable to acute ischemic stress; and (b) the level of the aforementioned threshold may increase progressively during the time course of ischemia in particular regions such as the hippocampus CA1 and CA3, suggesting that the duration of ischemia exerts a definite influence on the viability of the ischemic neuronal cells in these regions.
Failure of an Endothelin Antagonist to Modify Hypoperfusion after Transient Global Ischaemia in the Rat
Authors: Patel Toshal R. , McCulloch James
Published: November 2003

The role of endogenous endothelins in mediating postischaemic hypoperfusion after transient global ischaemia was investigated in halothane-anaesthetised rats. Pretreatment with the broad-spectrum (ETA and ETB) endothelin antagonist, Bosentan (17μmol/kg) had minimal effect on postischaemic hypoperfusion, measured by hydrogen clearance, in the caudate nucleus and the parietal cortex in the 3 h after bilateral common carotid artery occlusion with concomitant haemorrhagic hypotension (transient global ischaemia). In a separate series of rats with CBF measured by [14C]iodoantipyrine autoradiography at 90 min after carotid occlusion with concomitant haemorrhagic hypotension, Bosentan treatment failed to significantly alter CBF in any of the 35 brain regions examined. No significant alterations in CBF, measured by hydrogen clearance, were observed after transient bilateral common carotid artery occlusion. [14C]Iodoantipyrine autoradiography at 90 min after occlusion failed to demonstrate any significant increases in CBF after transient bilateral common carotid artery occlusion in any of the 35 brain regions examined in anaesthetised rats. The failure of the broad-spectrum endothelin antagonist Bosentan, at concentrations known to inhibit the cerebrovascular effects of exogenous ET-1, provide no support for the view that endothelins have a major role in mediating acute postischaemic hypoperfusion.
L-Arginine Does Not Restore Dilatation of the Basilar Artery during Diabetes Mellitus
Authors: Mayhan William G. , Didion Sean P. , Patel Kaushik P.
Published: November 2003

The goal of this study was to test the hypothesis that administration of L-arginine, a substrate for the synthesis of nitric oxide, restores endothelium-dependent dilatation of the basilar artery during diabetes mellitus. We measured the diameter of the basilar artery in vivo in nondiabetic and diabetic (streptozotocin; 50–60 mg/kg i.p.) rats in response to endothelium-dependent agonists (acetylcholine and bradykinin) and an endothelium-independent agonist (nitroglycerin) before and during application of L-arginine. Topical application of acetylcholine (1.0 and 10 μ M) and bradykinin (1.0 and 10 μ M) produced dilatation in nondiabetic rats of the basilar artery which was impaired in diabetic rats. Topical application of nitroglycerin (0.1 and 1.0 μ M) produced similar dilatation of the basilar artery in nondiabetic and diabetic rats. Topical application of L-arginine (0.1 and 3 m M) did not enhance dilatation of the basilar artery in response to acetylcholine and bradykinin in diabetic rats. Thus, impairment of dilatation of the basilar artery in diabetic rats in response to acetylcholine and bradykinin appears to be related to a mechanism unrelated to the availability of L-arginine for nitric oxide synthase.
Autoregulation in the Middle Meningeal Artery
Authors: Michalicek J. , Gordon V. , Lambert G.
Published: November 2003

In cats anesthetized with α-chloralose, auto-regulation of blood flow (F) in the middle meningeal and common carotid arteries was assessed by bleeding and subsequently reinfusing the animals to achieve a 25% step reduction in mean arterial blood pressure (P), while maintaining the systolic blood pressure >80 mmHg. The integrity of autoregulation was assessed by calculating the gain factor Gf = 1 — [(ΔF/F)/(ΔP/P)]. Cats were examined intact, after hexamethonium (10 mg/kg), and after papaverine (6 mg/kg). Reduction of blood pressure of 25 to 60 mmHg produced equivalent drops in carotid blood flow ( Gf = 0.041 ± 0.34; mean ± standard deviation, n = 12). There were only small changes in flow in the middle meningeal artery during this procedure ( Gf = 0.91 ± 0.29). Hexamethonium did not block autoregulation in the middle meningeal artery ( Gf = 0.92 ± 0.13, n = 4). However, papaverine almost completely abolished the ability of the artery to autoregulate ( Gf = 0.10 ± 0.16, n = 7). The results suggest that the middle meningeal artery possesses an ability similar to that of the cortical circulation to autoregulate its blood flow through intrinsic, non-neuronal mechanisms. This will have important implications for the study of disturbances of dural arterial control in migraine and other headaches.
L-NA-Sensitive rCBF Augmentation during Vibrissal Stimulation in Type III Nitric Oxide Synthase Mutant Mice
Authors: Ayata Cenk , Ma Jianya , Meng Wei , Huang Paul , Moskowitz Michael A.
Published: November 2003

Regional cerebral blood flow (rCBF) was studied in type III nitric oxide (NO) synthase (endothelial, eNOS) mutant and wild type mice during mechanical whisker stimulation before and after nitro-L-arginine (L-NA) superfusion using the closed cranial window technique. rCBF increased equally in cortical barrel fields in both strains during stimulation, as measured by laser Doppler-flowmetry, and was inhibited by L-NA superfusion (1 m M) in both groups. Hence, coupling of blood flow and metabolism appears neuronal NOS- (nNOS) but not eNOS-dependent in cortical barrel fields of the mouse.
Reduced Brain Edema and Infarction Volume in Mice Lacking the Neuronal Isoform of Nitric Oxide Synthase after Transient MCA Occlusion
Authors: Hara Hideaki , Huang Paul L. , Panahian Nariman , Fishman Mark C. , Moskowitz Michael A.
Published: November 2003

Infarct volume and edema were assessed after transient focal ischemia in mice lacking neuronal nitric oxide synthase (NOS) gene expression. With use of an 8–0 coated monofilament, the middle cerebral artery (MCA) of mutant (n = 32) and wild-type mice [SV-129 (n = 31), C57Black/6 (n = 18)] were occluded for 3 h and reperfused for up to 24 h. Regional CBF (rCBF), neurological deficits, water content, and infarct volume were examined in all three strains. rCBF, blood pressure, and heart rate did not differ between groups when measured for 1 h after reperfusion. Neurological deficits were less severe in mutant mice after MCA occlusion. Brain water content at 3 h after reperfusion and infarct volume at 24 h after reperfusion were greater in wild-type mice. These data indicate that genetic deletion of neuronal NOS confers resistance to focal ischemic injury in a reperfusion model. The findings agree with previous studies showing that tissue injury is less extensive after both permanent MCA occlusion and global ischemia in mice lacking neuronal NOS gene expression. Hence, NO may play a pivotal role in the pathogenesis of ischemic brain damage.
Relationship between Extracellular Glutamate Concentration and Voltage-Sensitive Calcium Channel Function in Focal Cerebral Ischemia in the Rat
Authors: Osuga Hitoshi , Hakim Antoine M.
Published: November 2003

Ischemic cell death occurs when extracellular glutamate levels increase, causing tissue depolarization and an excessive rise in intracellular calcium concentrations. The relative occurrence of the depolarization events and the changes in glutamate concentration in ischemia have not been studied. In a model of focal cerebral ischemia in the rat, three measurements were made simultaneously in vivo: cerebral blood flow (CBF) by the H2-clearance method, extracellular glutamate concentration by microdialysis, and activation of the voltage-sensitive calcium channel (VSCC) by its binding to [3H]nimodipine. Effects of probe implantation on these measurements were accounted for. The CBF to control ratio obtained during the experiments spanned the range of 1.08 to 0.07. Binding to [3H]nimodipine became significantly activated when CBF fell to ∼0.49 of its control value while extracellular glutamate concentrations increased significantly only at a CBF ratio of <0.33. Activation of the VSCC at this high CBF ratio may be due to ischemic depolarization, which has been shown to activate the binding to [3H]nimodipine. It may be useful to define a CBF threshold of 50% of normal in focal ischemia for opening of the VSCC. The same threshold has been linked to an overall depression of protein synthesis and to activation of a number of molecular responses.
Transport of D-Glucose and 2-Fluorodeoxyglucose across the Blood-Brain Barrier in Humans
Authors: Hasselbalch Steen G. , Knudsen Gitte M. , Holm Søren , Hageman L. Pinborg , Capaldo Brunella , Paulson Olaf B.
Published: November 2003

The deoxyglucose method for calculation of regional cerebral glucose metabolism by PET using 18F-2-fluoro-2-deoxy-d-glucose (FDG) requires knowledge of the lumped constant, which corrects for differences in the blood–brain barrier (BBB) transport and phosphorylation of FDG and glucose. The BBB transport rates of FDG and glucose have not previously been determined in humans. In the present study these transport rates were measured with the intravenous double-indicator method in 24 healthy subjects during normoglycemia (5.2 ± 0.7 m M). Nine subjects were restudied during moderate hypoglycemia (3.4 ± 0.4 m M) and five subjects were studied once during hyperglycemia (15.0 ± 0.7 m M). The global ratio between the unidirectional clearances of FDG and glucose (K1*/K1) was similar in normoglycemia (1.48 ± 0.22), moderate hypoglycemia (1.41 ± 0.23), and hyperglycemia (1.44 ± 0.20). This ratio is comparable to what has been obtained in rats. We argue that the global ratio is constant throughout the brain and may be applied for the regional determination of LC. We also determined the transport parameters of the two hexoses from brain back to blood and, assuming symmetrical transport across the BBB, we found evidence of a larger initial distribution volume of FDG in brain (0.329 ± 0.236) as compared with that of glucose (0.162 ± 0.098, p < 0.005). The difference can be explained by the very short experimental time, in which FDG may distribute both intra- and extracellularly, whereas glucose remains in a volume comparable to the interstitial fluid of the brain.
Endothelin-Mediated Vascular Tone following Focal Cerebral Ischaemia in the Cat
Authors: Patel Toshal R. , Galbraith Samuel , McAuley Moira A. , McCulloch James
Published: November 2003

The actions of Bosentan and PD155080, non-peptide endothelin receptor antagonists, were examined in feline pial arterioles in situ following middle cerebral artery (MCA) occlusion to gain insight into the cerebrovascular influence of endogenous endothelins in focal cerebral ischaemia. Immediately following permanent MCA occlusion, all pial arterioles overlying the suprasylvian and ectosylvian gyri displayed marked dilatations, which were maintained in a population of vessels but differentiated into sustained constrictions in others. Perivascular subarachnoid microinjections of Bosentan (30 μ M), PD155080 (30 μ M), and artificial CSF (pH 7.2) were performed between 30 and 210 min following MCA occlusion. The perivascular microapplication of Bosentan (30 μ M) and PD155080 (30 μ M) around pial vessels overlying the suprasylvian and ectosylvian gyri, which are within the territory of the occluded MCA, elicited an increase in the calibre of postocclusion dilated and constricted pial arterioles. The perivascular microapplication of PD155080 (30 μ/ M) around postocclusion constricted arterioles overlying the ectosylvian and suprasylvian gyri elicited an increase in the calibre of arterioles (69 ± 49% from preinjection baseline; n = 8). The perivascular microapplication of Bosentan (30 μ M) around postocclusion constricted arterioles overlying the ectosylvian and suprasylvian gyri also elicited an increase in the calibre of arterioles (68 ± 60% from preinjection baseline; n = 13). In contrast, the microapplication of CSF (pH 7.2) elicited small reductions in pial arteriolar calibre of postocclusion constricted arterioles (—8 ± 13% from preinjection baseline; n = 8). The perivascular microapplication of PD155080 (30 μ M) around postocclusion dilated pial arterioles overlying the ectosylvian and suprasylvian gyri elicited an increase in the calibre of arterioles (11 ± 10% from preinjection baseline; n = 38). The perivascular microapplication of Bosentan (30 μ M) around postocclusion dilated arterioles elicited an increase in the calibre of arterioles (16 ± 15% from preinjection baseline; n = 36). In contrast, the microapplication of CSF (pH 7.2) elicited small reductions in pial arteriolar calibre of postocclusion dilated arterioles (—9 ± 6% from preinjection baseline; n = 44). Perivascular microapplication of Bosentan or PD155080 had minimal effect on the calibre of pial arterioles on the parasagittal gyrus (anterior cerebral artery territory), although these arterioles had also displayed sustained dilatation following MCA occlusion. These results indicate that contractile factors (whose effects can be reversed with endothelin receptor antagonists) constrict or impair dilatation of cortical resistance arterioles in an acute cerebral ischaemic episode.
Local Cerebral Blood Flow in a Rat Cortical Vein Occlusion Model
Authors: Nakase H. , Heimann A. , Kempski O.
Published: November 2003

The symptoms following sinus and vein occlusion observed in patients and experimental animals display a considerable variability that so far remains largely unexplained. In a rat cortical vein occlusion model using a photochemical thrombotic technique, we examined changes in the cerebral venous flow pattern by fluorescence angiography and regional cerebral blood flow (rCBF) and cerebral blood volume fraction (CBVF) by a modern laser Doppler “scanning” technique. Brain damage was assessed histologically. Fluorescence angiographic findings fell into two groups: group A, rats with an altered venous flow pattern after occlusion (n = 12), and group B, rats with interruption of blood flow and/or a growing venous thrombus (n = 5). In addition, sham-operated animals made up group C (n = 5). Extravasation of fluorescein, a massive decrease in rCBF, a short-lasting increase in CBVF, and regional brain damage were typical for group B. In addition, cortical CBF mapping revealed a transient hyperperfusion zone with hyperemia surrounding a hypoperfused ischemic core in group B. A circulation perturbation following venous occlusion appeared near those occluded cerebral veins without sufficient collateral flow. Furthermore, the venous thrombus continued to grow, accompanied by local critical ischemia and severe brain damage. Conversely, 71% of the animals (12 of 17) tolerated occlusion of a solitary vein without major flow disturbances or histological evidence of damage to the CNS (group A).
Thrombin Stimulates Activation of the Cerebral 5-Lipoxygenase Pathway during Blood-Brain Cell Contact
Authors: Winking Michael , Heldt Rochus M. , Simmet Thomas
Published: November 2003

The purpose of this study was to identify the trigger mechanism activating the 5-lipoxygenase pathway during blood–brain cell contact and to estimate the contribution of blood and brain cells to the cysteinyl–leukotriene (LT) biosynthesis observed under these conditions. Incubation of dissociated rat brain cells in Krebs-Henseleit solution for up to 60 min did not stimulate any detectable cysteinyl–LT biosynthesis. Incubation of recalcified rat whole blood in vitro for up to 60 min led to release of only small amounts of cysteinyl–LT into the serum samples. However, coincubation of dissociated rat brain cells with physiologically recalcified autologous whole blood triggered a time-dependent release of large amounts of immunoreactive cysteinyl–LT into the serum samples. By reverse-phase HPLC, immunoreactive cysteinyl–LT was identified as a mixture of LTC4, LTD4, and LTE4. The extent of the 5-lipoxygenase stimulation depended on the amount of autologous blood coincubated with the dissociated brain cells. Activation of the 5-lipoxygenase pathway also occurred with coincubation of dissociated rat brain cells with recalcified autologous plasma. Stimulation of cysteinyl–LT biosynthesis during blood–brain cell contact remained unaffected by aprotinin, but concentration-dependent inhibition by the structurally and functionally unrelated thrombin inhibitors D-Phe-Pro-Arg-CH2Cl and recombinant hirudin was seen. Finally, when dissociated rat brain cells were incubated in Krebs-Henseleit solution in the presence of human α-thrombin, a concentration-dependent release of cysteinyl–LT into the buffer samples was observed. These data demonstrate that, in rats, during blood–brain cell contact, stimulation of the 5-lipoxygenase pathway in brain cells proceeds via α-thrombin as effector molecule.
Sample Size and Statistical Power in [15O]H2O Studies of Human Cognition
Authors: Andreasen Nancy C. , Arndt Stephan , Cizadlo Ted , O'Leary Daniel S. , Watkins G. Leonard , Ponto Laura L. Boles , Hichwa Richard D.
Published: November 2003

Determining the appropriate sample size is a crucial component of positron emission tomography (PET) studies. Power calculations, the traditional method for determining sample size, were developed for hypothesis-testing approaches to data analysis. This method for determining sample size is challenged by the complexities of PET data analysis: use of exploratory analysis strategies, search for multiple correlated nodes on interlinked networks, and analysis of large numbers of pixels that may have correlated values due to both anatomical and functional dependence. We examine the effects of variable sample size in a study of human memory, comparing large (n = 33), medium (n = 16,17), small (n = 11, 11, 11), and very small (n = 6, 6, 7, 7, 7) samples. Results from the large sample are assumed to be the “gold standard.” The primary criterion for assessing sample size is replicability. This is evaluated using a hierarchically ordered group of parameters: pattern of peaks, location of peaks, number of peaks, size (volume) of peaks, and intensity of the associated t (or z) statistic. As sample size decreases, false negatives begin to appear, with some loss of pattern and peak detection; there is no corresponding increase in false positives. The results suggest that good replicability occurs with a sample size of 10–20 subjects in studies of human cognition that use paired subtraction comparisons of single experimental/baseline conditions with blood flow differences ranging from 4 to 13%.
Age Dependence of Total Cerebral Blood Flow Volume from Childhood to Adulthood
Authors: Schöning Martin , Hartig Bernd
Published: November 2003

In a prospective study of the natural development of total cerebral blood flow volume (CBFV), the common, external and internal carotid and vertebral arteries were examined in 94 healthy children and adolescents between 3 and 18 years of age (sex and age evenly distributed) using a 7.0-MHz transducer of a computed sonography system. Intravascular flow volumes were calculated with the product of angle-corrected time-averaged flow velocity and the cross-sectional area of the vessel. CBFV was determined as the sum of flow volumes in the internal carotid and vertebral arteries of both sides. CBFV increased significantly between 3 and 6.5 years of age (from 687 ± 85 to 896 ± 110 ml/min; age correlation, p ≤ 0.01) and declined thereafter ( p ≤ 0.001) to a constant level of ∼700 ml/min at 15 years of age. There was no difference in CBFV between sexes. The proportion of bilateral vertebral artery flow volume in total CBFV decreased significantly between the ages of 3 and 18 years ( p ≤ 0.001). As the flow volumes of the external carotid arteries increased markedly from childhood to adulthood, flow volumes of the common carotid arteries were not representative of CBFV. Intrasession test-retest correlation of CBFV was high ( r = 0.89, p ≤ 0.0001). Reference data for the childhood years presented here and previously described results from healthy adults allow us to outline the natural evolution of CBFV in humans. The reliability of the method has already been demonstrated. Thus, it may now be introduced into clinical application.
High Temporal Resolution Diffusion MRI of Global Cerebral Ischemia and Reperfusion
Authors: Pierpaoli Carlo , Alger Jeffry R. , Righini Andrea , Mattiello James , Dickerson Russell , Pres Daryl Des , Barnett Alan , Chiro Giovanni Di
Published: November 2003

Although brain ischemia has been extensively studied using diffusion-weighted magnetic resonance imaging, most studies performed so far have not had adequate time resolution to follow the temporal changes in the water apparent diffusion coefficient (ADC) in hyperacute ischemia. Using diffusion echo planar imaging, we obtained ADC maps (calculated from measurements made with 8 b-values) with a time resolution of 43 s in a feline model of global brain ischemia and reperfusion. Different protocols were performed: 10-min hypoperfusion, 10- and 22-min ischemia followed by reperfusion, and cardiac arrest. ADC values were obtained from white matter of the internal capsule and from the thalamus. Cortical gray matter measurements were not deemed reliable due to the close proximity of CSF in the cortical sulci. Following occlusion, the ADC declined in the thalamus to <2 SD of its normal baseline value within 1.5–2.5 min. This decay was exponential with a time constant (τ ± SD) of 6.0 ± 2.6 min; no further decrease in the ADC was observed 10 min following ischemia. Following reperfusion, in animals that showed ADC recovery, the ADC began increasing immediately, returning to its preischemic value in ∼15 min. No significant ADC changes were observed during hypoperfusion. Following cardiac arrest, the decay of ADC was more rapid in the thalamus (τ = 2.6 ± 0.6 min) than in white matter (τ = 6.6 ± 1.8 min). We observed that the ADC at 40 min after cardiac arrest was similar to the ADC at 10 min after ischemia. Given that all animals subjected to 10-min ischemic episodes showed ADC recovery with reperfusion, doubt is cast on whether it is possible to define a threshold value of the ADC below which brain tissue is irreversibly damaged. Finally, despite variability in the time constants of the ADC decay induced by ischemia, the ADC values at 10 min were very similar in all the animals. This suggests that when blood flow is diminished sufficiently to induce an ADC reduction, differences in perfusion affect the rapidity of the decrease but not the final asymptotic value reached.
Neuronal Hyperexcitability and Reduction of GABAA-Receptor Expression in the Surround of Cerebral Photothrombosis
Authors: Schiene Klaus , Bruehl Claus , Zilles Karl , Qu Meishu , Hagemann Georg , Kraemer Matthias , Witte Otto W.
Published: November 2003

Changes of neuronal excitability and γ-aminobutyric acid (GABAA)-receptor expression were studied in the surround of photothrombotic infarcts, which were produced in the sensorimotor cortex of the rat by using the rose bengal technique. In a first series of experiments, multiunit recordings were performed on anesthetized animals 2–3 mm lateral from the lesion. Mean discharge frequency was considerably higher in recordings from lesioned animals (>100 Hz in the first postlesional week) compared with control animals (mean, 15 Hz). These alterations were already present after 1 day but were most pronounced 3 to 7 days after lesion induction. Thereafter the hyperexcitability declined again, although it remained visible up to 4 months. In a second series of experiments, the GABAA-receptor expression was studied autoradiographically. This revealed a reduction of GABAA receptors in widespread brain areas ipsilateral to the lesion. The reduction was most pronounced in the first days after lesion induction and declined with longer intervals. It is concluded that cortical infarction due to photothrombosis leads to a long-lasting and widespread reduction of GABAA-receptor expression in the surround of the lesion, which is associated with an increased neuronal excitability. Such alterations may be responsible for epileptic seizures that can be observed in some patients after stroke and may contribute to neurologic deficits after stroke.
Neuroprotective Effects of Human Recombinant Interleukin-1 Receptor Antagonist in Focal Cerebral Ischaemia in the Rat
Authors: Loddick Sarah A. , Rothwell Nancy J.
Published: November 2003

Recombinant human interleukin-1 receptor antagonist (rhIL-1ra) markedly protects against focal cerebral ischaemia in the rat, implicating endogenous IL-1 in the events leading to cerebral infarction. The present experiments investigated the effect of intracerebroventricular (i.c.v.) administration of IL-1β or rhIL-1ra on ischaemia damage and physiological parameters after permanent middle cerebral artery occlusion in the rat. IL-1β (5 ng, i.c.v.) markedly (92%) enhanced infarct volume and caused a significant rise in body temperature, but rhIL-1ra (10 μg, i.c.v.) significantly reduced infarct volume and did not significantly affect heart rate, blood pressure, or body temperature. rhIL-1ra administered 30 min before, or at the time of ischaemia significantly reduced infarct volume in cortex (55 and 60%, respectively) and striatum (52 and 41%, respectively). rhIL-1ra administered 30 min after ischaemia significantly reduced total and cortical infarct volume (26 and 29%, respectively), but did not significantly protect striatal tissue. The effects of rhIL-1ra were still evident in both cortex and striatum 7 days after ischaemia. These results support the role of IL-1 in ischaemic brain damage, revealing potent, sustained, neuroprotective effects of rhIL-1ra in the cortex and striatum, which cannot be attributed directly to changes in physiological parameters.
Neuroprotective Effect of YM90K, a Novel AMPA/Kainate Receptor Antagonist, in Focal Cerebral Ischemia in Cats
Authors: Yatsugi S. , Takahashi M. , Kawasaki-Yatsugi S. , Koshiya K. , Sakamoto S. , Uematsu D. , Shimizu-Sasamata M.
Published: November 2003

We studied the effect of a novel α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)/kainate antagonist, YM90K [6-(1 H-imidazol-1-yl)-7-nitro-2, 3(1 H, 4 H)-quinoxalinedione monohydrochloride], in a focal cerebral ischemia model using anesthetized cats. Cats were subjected to permanent occlusion of the middle cerebral artery (MCA) for 6 h, then killed and examined histologically. The amount of ischemic damage was assessed in 12 stereotaxic coronal sections. Treatment with YM90K (i.v. infusion of 0.5 mg/5 ml/kg/h) starting 10 min after MCA occlusion markedly reduced the volume of ischemic damage (from 2823 ± 164 mm3 of the cerebral hemisphere in saline-treated cats to 1737 ± 305 mm3 in YM90K-treated cats). No essential differences were observed between YM90K- and saline-treated cats concerning physiological variables or brain temperature. These results further support the notion that the AMPA/kainate receptor plays an important role in the pathogenesis of focal cerebral ischemia. This evidence for the neuroprotective efficacy of YM90K in a gyrencephalic species suggests its therapeutic potential in the treatment of human stroke.
Spatial Memory Disturbance after Focal Cerebral Ischemia in Rats
Authors: Yonemori Fumihiko , Yamada Hideki , Yamaguchi Tohru , Uemura Atsuhiro , Tamura Akira
Published: November 2003

We investigated the impairment of retention of spatial memory in rats with chronic focal cerebral ischemia, and examined the correlation between this impairment and pathological outcomes. A preoperative acquisition trial of the Morris water-maze task was performed twice a day for 14 successive days, and then the middle cerebral artery (MCA) was occluded. A retention trial was performed 8 weeks after MCA occlusion. Escape latency and swimming path length to the platform were significantly increased in MCA-occluded rats compared with those of sham-operated rats, and these deficits significantly correlated with massive shrinkage of the brain. Retention latency of a passive avoidance task, which was trained preoperatively, was also significantly shortened in MCA-occluded rats compared with that in sham-operated rats. These results suggest that chronic focal cerebral ischemia causes prolonged spatial memory disturbance in rats and is associated with pathological changes, and that this rat model may be useful for assessing not only anterograde but also retrograde amnesia caused by focal cerebral ischemia.
Effects of Metrifonate, a Cholinesterase Inhibitor, on Local Cerebral Glucose Utilization in Young and Aged Rats
Authors: Bassant M. H. , Jazat-Poindessous F. , Lamour Y.
Published: November 2003

The effects of the centrally acting anticholinesterase metrifonate (MFT) and its metabolite dichlorvos (2,2-dichlorovinyl dimethyl phosphate; DDVP) on local cerebral glucose utilization (LCGU) have been studied in 3- and 27-month-old rats, using the autoradiographic [14C]deoxyglucose technique. In 3-month-old rats, MFT (80 mg/kg i.p.) increased LCGU significantly in 17 of the 54 regions studied, including insular, cingulate, and temporal cortices, ventral hippocampus, thalamus, lateral habenula, substantia nigra, and superior colliculus. In these regions, the average MFT-induced increase in LCGU was 23% above control. The average hemispheric LCGU increased by 10% (p < 0.01). DDVP (5 mg/kg) increased LCGU in 19 regions (average increase 26%). The average hemispheric LCGU increased by 9% (p < 0.01). Regional distributions of MFT- and DDVP-induced increases in LCGU were similar and overlapped the distribution of the acetylcholinesterase activity. In 27-month-old rats, MFT was active in 18 regions (average increase 25%). The whole-brain mean LCGU increased by 10% (p < 0.01). MFT compensated for the age-related hypometabolism in some brain areas including insular, temporal, and retrosplenial cortices, substantia nigra, and superior colliculus. The effects of MFT on LCGU were preserved in old rats, at variance with other anticholinesterases (tacrine, physostigmine), which are less active in the aged rat brain.