bluuebunny/crossref_metadata_2025 huggingface dataset:
Adenosine Receptor Blockade Augments Interstitial Fluid Levels of Excitatory Amino Acids during Cerebral Ischemia
Authors: Sciotti Veronica M. , Roche Francis M. , Grabb Margaret C. , Van Wylen David G. L.
Published: April 2011

The excitotoxic hypothesis suggests that cerebral ischemic damage results in part from the accumulation of the excitatory and potentially toxic neurotransmitters glutamate and aspartate. Adenosine, which also increases during cerebral ischemia, is proposed to inhibit neurotransmitter release. The purpose of this study was to determine if adenosine receptor blockade exacerbates the accumulation of glutamate and aspartate during cerebral ischemia. Microdialysis probes, implanted bilaterally in the caudate nucleus of halothane-anesthetized rats, were used to (1) assess changes in interstitial fluid (ISF) glutamate, aspartate, adenosine, and adenosine metabolites; (2) measure local cerebral blood flow (H2 clearance); and (3) deliver 8-( p-sulfophenyl)theophylline (SPT), an adenosine receptor antagonist, locally to the brain. The probe on one side of the brain was perfused with artificial cerebrospinal fluid (CSF) containing 10−3 M SPT, while the probe on the opposite side received only artificial CSF. Animals were exposed to 20 min of ischemia (carotid occlusion + arterial blood pressure = 50 mm Hg) followed by 60 min of reperfusion. Dialysate glutamate and aspartate increased during and after cerebral ischemia, but were increased to a greater extent in the presence of adenosine receptor blockade. Likewise, the increase in dialysate adenosine and adenosine metabolites was enhanced on the side of locally administered SPT. These data suggest that endogenous adenosine attenuates the accumulation of glutamate and aspartate during cerebral ischemia.
Regulation of Cortical Blood Flow by the Dorsal Raphe Nucleus: Topographic Organization of Cerebrovascular Regulatory Regions
Authors: Underwood Mark D. , Bakalian Mihran J. , Arango Victoria , Smith Robert W. , Mann J. John
Published: April 2011

We examined in rat: (1) the time-course and magnitude of change in cortical blood flow (CoBF) following electrical stimulation of the dorsal raphe nucleus (DRN) and (2) whether DRN lesions affect resting CoBF or the cerebrovascular response to CO2. Animals were anesthetized (chloralose), paralyzed, and artificially ventilated. The effect of stimulus frequency (1–200 Hz) and intensity (10–100 μA) on arterial pressure, heart rate, and CoBF was examined; lesions were made electrolytically. CoBF was measured using a laser-Doppler flowmeter with the probe placed extradurally over the parietal sensorimotor cortex. The DRN was computer reconstructed in three dimensions from Nissl stained coronal sections for localization of electrode placements. Brief stimuli (8 s; n = 6) elicited frequency and intensity-dependent increases in arterial pressure, heart rate, and CoBF. Sustained intermittent trains of stimuli of rostral DRN (200 Hz; 1 s on/1 s off; 70 μA) elicited a decrease (85 ± 12% of baseline; n = 9) in CoBF ( p < 0.05) while stimulation in caudal DRN resulted in increased CBF (126 ± 13% of baseline; n = 9). Phenylephrine infusion (0.1–1 μg; i.v.; n = 8) increased arterial pressure and CoBF less than that elicited by brief DRN stimulation ( p < 0.05). DRN lesions did not affect resting CoBF (140 ± 25 perfusion units (PU) before; 127 ± 16 PU after DRN lesion; p > 0.05, n = 5) or mean arterial pressure (127 ± 13 before; 120 ± 11 after); nor did it affect the cerebrovascular response to change in arterial Pco2. Sustained intermittent stimulation of the DRN can evoke either increases or decreases in CoBF depending on the anatomical sublocalization. The DRN does not tonically maintain resting CoBF, nor participate in the cerebrovascular response to change in Pco2.
Rapid Autoregulation of Cerebral Blood Flow: A Laser-Doppler Flowmetry Study
Authors: Florence Geneviève , Seylaz Jacques
Published: April 2011

The mechanisms underlying autoregulation of CBF were studied in 19 rabbits using laser-Doppler flowmetry. A cranial plexiglas window was chronically inserted in the skull with dental cement under general anesthesia. The animals then were reanesthetized 5–7 days later and subjected to aortic bleeding while CBF was measured with the probe placed on the window. In the first set of experiments, MABP was decreased (from 90 to 30 mm Hg) and was maintained constant for 1 min. During the first seconds, CBF followed the steep decrease of MABP. Then, CBF increased and reached a plateau within 3–13 s, depending on the severity of hypotension. Hyperemia occurred when blood was restored, and the CBF recovered from this posthypotensive hyperemia with a rapid phase (within 2 s) and a slow phase (total recovery within 1 min). The lower limit of autoregulation was found to be 40 mm Hg. An increase in CBF due to papaverine showed that vasodilation was not maximal below this limit. In the second set of experiments, the rabbits were subjected to four episodes of hypotension at 40 mm Hg each but of different durations (from 2–3 to 60 s). The posthypotensive hyperemia was not influenced by the duration of hypotension, but the time of the total recovery phase increased with the duration of hypotension. We conclude that there exist rapid adaptive mechanisms leading to autoregulation and that the vasodilation is not dependent upon the duration of hypotension.
Attenuated Development of Ischemic Brain Edema in Vasopressin-Deficient Rats
Authors: Dickinson Lawrence D. , Betz A. Lorris
Published: April 2011

Brain edema formation was investigated in the vasopressin-deficient Brattleboro rat using a middle cerebral artery occlusion model of early ischemic injury. Water and sodium accumulation after 4 h of ischemia were attenuated 36 and 20%, respectively, in the Brattleboro strain as compared to the control Long–Evans strain. This effect was independent of differences in animal size and state of hydration. In addition, measurements of cerebral blood flow indicated that Brattleboro and Long–Evans rats had equal levels of ischemia following middle cerebral artery occlusion. Systemic treatment of Brattleboro rats with vasopressin normalized their serum electrolyte concentrations and osmolarity but did not alter sodium or water accumulation in the ischemic brain. In contrast, intraventricular administration of vasopressin in Brattleboro rats increased edema formation to that seen in control rats. The reduced water and sodium accumulation in Brattleboro rats subjected to middle cerebral artery occlusion may be related to alterations in blood–brain barrier permeability since the blood-to-brain sodium flux was 36% less in the ischemic tissue of the Brattleboro as compared to the Long–Evans strain. These results support the hypothesis that central vasopressin is a regulator of brain volume and electrolyte homeostasis. Furthermore, our findings suggest a role for central vasopressin in the development of ischemic brain edema.
Effect of Atriopeptin on Production of Cerebrospinal Fluid
Authors: Schalk Kimberly A. , Faraci Frank M. , Williams John L. , VanOrden Dianna , Heistad Donald D.
Published: April 2011

We reported previously that intravenous infusion of atriopeptin increases blood flow to the choroid plexus. The first goal of this study was to determine whether blood-borne atriopeptin increases the production of CSF. Ventriculocisternal perfusion was used to measure the production of CSF in anesthetized rabbits. Atriopeptin increased blood flow to the choroid plexus (measured with microspheres) but did not alter the production of CSF. The second goal of the study was to determine whether intracerebroventricular injection of atriopeptin affects the production of CSF. Injection of atriopeptin into the cerebral ventricles increased blood flow to the choroid plexus but produced a small decrease in production of CSF. In summary, blood-borne and intraventricular atriopeptin increase blood flow to the choroid plexus, but do not increase the production of CSF.
Secobarbital Attenuates Excitotoxicity but Potentiates Oxygen—Glucose Deprivation Neuronal Injury in Cortical Cell Culture
Authors: Giffard Rona G. , Weiss John H. , Swanson Raymond A. , Choi Dennis W.
Published: April 2011

We examined the effects of secobarbital and other sedative-hypnotic barbiturates on the neuronal death induced by exposure to excitatory amino acids or deprivation of oxygen or glucose in mouse cortical cell cultures. N-Methyl-d-aspartate (NMDA), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate, and kainate toxicities were attenuated in a concentration-dependent fashion by high concentrations of secobarbital or thiopental. Antagonism of NMDA toxicity was not overcome by increasing NMDA concentration and not mimicked by γ-aminobutyrate. Despite these antiexcitotoxic actions, secobarbital exacerbated the neuronal death induced by deprivation of either glucose alone or oxygen and glucose together; death induced by oxygen deprivation alone was little affected. Thiopental and methohexital also increased oxygen-glucose deprivation injury. A possible explanation for this injury potentiation was provided by the observation that secobarbital enhanced the cellular ATP depletion induced by combined oxygen-glucose deprivation. Deleterious effects on ATP production may counterbalance the protective effects of barbiturates under some conditions.
Striatal 18F-DOPA Uptake: Absence of an Aging Effect
Authors: Eidelberg D. , Takikawa S. , Dhawan V. , Chaly T. , Robeson W. , Dahl R. , Margouleff D. , Moeller J. R. , Patlak C. S. , Fahn S.
Published: April 2011

l-[18F]6-Fluoro-DOPA (l-[18F]6-fluoro-3,4-dihydroxyphenylalanine; FDOPA) has been used with quantitative positron emission tomography (PET) to assess presynaptic nigrostriatal dopaminergic function in life. The relationship of estimated kinetic rate constants for striatal FDOPA uptake [ Ki(FDOPA)] to the normal aging process has been the subject of conflicting reports. Resolution of this issue has been hampered by methodological differences in previous FDOPA/PET investigations. We studied 19 healthy normal subjects (aged 27–77 years) and measured striatal Ki-(FDOPA) according to each of the earlier methods. While significant correlations (p < 0.005) existed between Ki(FDOPA) values estimated by the various techniques, none correlated with normal aging. We conclude that normal striatal Ki(FDOPA) values estimated using quantitative FDOPA/PET are uncorrelated with the aging process.
Flunarizine Blocks Elevation of Free Cytosolic Calcium in Synaptosomes following Sustained Depolarization
Authors: Cohan Stanley L. , Redmond David J. , Chen Mei , Wilson Dahlia , Cyr Philip
Published: April 2011

Gerbil cerebral cortical synaptosomes loaded with the fluorescent calcium probe FURA-2 were used to study depolarization-induced presynaptic cytosolic free calcium concentration, as an in vitro model of cerebral ischemia. The depolarization-induced increase in intrasynaptosomal cytosolic free calcium concentration is not sodium-dependent or sodium channel-dependent and may be due to an influx of extrasynaptosomal calcium resulting from a cadmium- and omega-conotoxin-sensitive, nickel-, nifedipine-, and nimodipine-insensitive voltage-regulated channel. The depolarization-induced increase in intrasynaptosomal free cytosolic calcium concentration is also inhibited by flunarizine, a calcium antagonist that has protective effects in animal models of cerebral anoxia and ischemia. Our results suggest that presynaptic calcium uptake following depolarization may be mediated in part by an N-type channel. Flunarizine may block presynaptic calcium accumulation, in part, by blocking this N-type channel; this blockade may be just one of several mechanisms by which flunarizine exerts protective effects following cerebral ischemia.
Brain Calcium Metabolism in Hypoglycemic Coma
Authors: Kristián Tibor , Gidö Gunilla , Siesjö Bo K.
Published: April 2011

The present experiments were designed to provide information on brain calcium metabolism during hypoglycemic coma. We specifically wished to evaluate changes in extracellular calcium concentration (Ca2+e) during prolonged hypoglycemic coma and recovery and to assess whether Ca2+e falls to similar values during hypoglycemia and ischemia. To that end, Ca2+e and K+e in neocortical tissue were recorded by ion-sensitive microelectrodes during hypoglycemic coma of 30 min duration and during 15 min of recovery. Cardiac arrest ischemia was induced either at the end of the period of hypoglycemia or after 15 min of recovery. Hypoglycemic coma, as reflected by a DC potential shift and by cellular release of K+, was accompanied by a sustained decrease in Ca2+e from ∼1.2 to ∼0.02 m M, i.e., to ∼1% of control. Infusion of glucose was followed by a biphasic recovery of Ca2+e, starting within 2 min of infusion. During the first phase, completed within the initial 3–4 min, Ca2+e rose to about 25% of control. During the second phase, Ca2+e slowly increased toward normal within 25–30 min. Ischemia, when induced at the end of the period of hypoglycemia, was accompanied by a rise in Ca2+e to about 0.1 m M, i.e., about 10% of control. A similar value was recorded when ischemia was induced after 15 min of recovery following a 30-min hypoglycemic coma. Although the present results do not give information on Ca2+i during hypoglycemic coma, it is tempting to conclude that partial preservation of the nucleoside triphosphate stores, and absence of acidosis, allow some binding and sequestration of the calcium entering the cell. Such binding and sequestration may explain the pronounced biphasic nature of the recovery curves for Ca2+e. Thus, if one assumes that the rapid increase in Ca2+e represents extrusion of available “free” intracellular Ca2+, one can envisage that the slow phase of recovery represents calcium that is slowly extruded following its release from the binding and sequestration stores.
Inhibition of Nitric Oxide Synthase Attenuates the Cerebral Blood Flow Response to Stimulation of Postganglionic Parasympathetic Nerves in the Rat
Authors: Morita-Tsuzuki Yoko , Hardebo Jan Erik , Bouskela Eliete
Published: April 2011

Stimulation of cerebrovascular parasympathetic nerves markedly increases cortical blood flow. Nitric oxide (NO) or a NO-containing compound is present in these nerves and may therefore, upon release, be partly responsible for the flow increase. In addition, transmitters released from the nerves may cause synthesis and release of this compound from the endothelium. The contribution of NO synthesis to the cortical blood flow (CoBF) increase during parasympathetic stimulation was elucidated in rat by laser–Doppler flowmetry. Thirty-minute exposure to circulating Nω-nitro-l-arginine methyl ester (l-NAME) 50 mg kg−1 eliminated most of the response (from 104 to 8% increase), whereas 10-min exposure to this dose or 30-min exposure to 5 mg kg−1 caused a less marked reduction. The reducing effect was particularly evident after elimination of the systemic blood pressure increase caused by l-NAME (only 3% increase after the high dose). Infusion of l-arginine restored the flow response. Resting CoBF was not substantially affected by blockade of NO formation. Thus, release of an NO-containing compound constitutes a major component of the increase in CoBF caused by parasympathetic nerve stimulation but does not seem to contribute to cortical flow regulation during resting conditions.
Time Course of Hippocampal Glucose Utilization and Persistence of Parvalbumin Immunoreactive Neurons after Ibotenic Acid—Induced Lesions of the Rat Dentate Area
Authors: Wree Andreas , Erselius Ralf , Tønder Niels , Beck Thomas
Published: April 2011

The effects of ibotenic acid induced lesions of the dentate gyrus on hippocampal glucose utilization and parvalbumin-positive neurons were evaluated in male Wistar rats. Ibotenic acid was injected in the right dorsal dentate gyrus. Quantification of glucose utilization was performed 3 days, 3 weeks, or 3 months after the lesion using the 14C-2-deoxyglucose method. Nissl-stained sections and sections stained for acetylcholinesterase were used as references for anatomical delineation of the hippocampal cytoarchitecture. Additional sections were stained for parvalbumin. The results revealed widespread reductions of glucose utilization in all layers and sectors of the hippocampus in the ipsilateral lesioned hemisphere and also in the nonlesioned contralateral hemisphere. The reductions occurred as early as 3 days after the lesion and persisted up to 3 months. In neither hippocampal structure did glucose utilization return to control levels. Immunohistochemical visualization of parvalbumin-containing neurons revealed that these putatively inhibitory neurons persisted in the otherwise granule-cell-depleted area. The data show that interruption of the excitatory trisynaptic pathway from the entorhinal cortex to the CA1 at the level of the dentate gyrus affects hippocampal glucose utilization irreversibly and uniformly. Since some inhibitory neurons seem to survive the ibotenic acid lesion, we suggest that the reductions of hippocampal glucose utilization reflect an imbalance in favor of inhibitory neurons in the ipsilateral hippocampus after the lesion, which manifests also in the contralateral hemisphere via the commissural pathways.
Reductions in Focal Ischemic Infarctions Elicited from Cerebellar Fastigial Nucleus Do Not Result from Elevations in Cerebral Blood Flow
Authors: Yamamoto Seiji , Golanov Eugene V. , Reis Donald J.
Published: April 2011

To determine whether the neuroprotection elicited from electrical stimulation of the cerebellar fastigial nucleus (FN) is attributable to the elevation in regional cerebral blood flow (rCBF), we compared the effects in spontaneously hypertensive rats of stimulation of the rostral ventrolateral medulla (RVL) or FN on (a) a focal ischemic lesion produced by middle cerebral artery (MCA) occlusion, and (b) the changes in rCBF, measured by laser-Doppler flowmetry for 1.5 h, over regions corresponding to the ischemic core (parietal cortex), penumbra (occipital cortex), and nonischemic area (contralateral parietal cortex). Stimulation of FN for 1 h following MCA occlusion reduced infarction 24 h later by 52%. Stimulation of RVL was ineffective. Changes in the lesion were confined to the penumbra. FN and RVL stimulation comparably and significantly increased rCBF up to 185% in unlesioned animals. Following MCA occlusion, stimulation of FN or RVL and hypercarbia failed to elevate rCBF in the ischemic area but did so in the nonischemic area, even though in the same animals only FN stimulation reduced infarction 24 h later. We conclude that (a) the neuroprotection elicited from FN is not the result of an increase in rCBF but results from another mechanism, possibly reduction of metabolism in penumbra, and (b) the pathways mediating central neurogenic vasodilation and neuroprotection are, in part, distinct.
In vitro Model of Hypoxia: Basic Fibroblast Growth Factor Can Rescue Cultured CNS Neurons from Oxygen-Deprived Cell Death
Authors: Akaneya Yukio , Enokido Yasushi , Takahashi Mitsuo , Hatanaka Hiroshi
Published: April 2011

We established an in vitro hypoxia model and investigated the protective effect of basic fibroblast growth factor (bFGF) against neuronal cell death caused by hypoxia. Hippocampal neurons obtained from rats on embryonic day (E) 17 and 20 and on postnatal day (P) 4 were cultured for 6–24 h in an oxygen-deprived state. This in vitro hypoxia study showed that the cultured neurons were sensitive to the oxygen deprivation. The cultured P4 rat hippocampal neurons seemed to be weaker in the hypoxia condition than those of E17 and E20 rats, suggesting that the cultured postnatal cells might be sensitive to hypoxia. bFGF, but not nerve growth factor, prevented the neuronal cell death caused by hypoxia in a dose-dependent manner.
Endothelin-1-Induced Reductions in Cerebral Blood Flow: Dose Dependency, Time Course, and Neuropathological Consequences
Authors: Macrae I. Mhairi , Robinson Michael J. , Graham David I. , Reid John L. , McCulloch James
Published: April 2011

The capacity of endothelin-1 to induce severe reductions in cerebral blood flow and ischaemic neuronal damage was assessed in anaesthetised rats. Endothelin-1 (25 μl of 10−7–10−4 M) was applied to the adventitial surface of an exposed middle cerebral artery and striatal blood flow assessed by the hydrogen clearance technique. Endothelin-1 induced severe dose-dependent reductions in cerebral blood flow (e.g., minimum CBF at 10−5 M of 9 ± 11 ml 100 g−1 min−1 compared to 104 ± 22 ml 100 g−1 min−1 with vehicle, p < 0.05), which persisted for at least 60 min at each concentration of endothelin-1. Application of endothelin-1 to the middle cerebral artery produced dose-dependent ischaemic brain damage (e.g., volume of damage of 65 ± 34 mm3 at 10−5 M compared to 0.22 ± 0.57 mm3 for vehicle, p < 0.01). These data demonstrate that endothelin-1 is capable of reducing blood flow to pathologically low levels and provide a new model of controlled focal ischaemia followed by reperfusion.
Selective Loss and Selective Sparing of Neurons in the Thalamic Reticular Nucleus following Human Cardiac Arrest
Authors: Ross Douglas T. , Graham David I.
Published: April 2011

Neurons in the portion of the human thalamic reticular nucleus (RT) associated with the prefrontal cortex and mediodorsal thalamic nuclei were found to be selectively vulnerable to ischemic neuronal damage following relatively short (≤5-min) duration cardiac arrest. In contrast, selective sparing of these RT neurons occurred in cases with longer (>10-min) duration of arrest that was sufficient to produce extensive ischemic neuronal damage throughout the cerebral cortex and thalamic relay nuclei. The selective degeneration of RT neurons appears to require the sustained activity of corticothalamic or thalamocortical projections to the RT following the ischemic insult. Loss of RT neurons associated with the frontal cortex and mediodorsal thalamus may be the biological basis of some types of persisting cognitive deficits in attentional processing experienced by patients following cardiac arrest, open heart surgery, or other forms of brief global cerebral ischemia.
6-[18F]fluoro-l-DOPA Metabolism in Living Human Brain: A Comparison of Six Analytical Methods
Authors: Hoshi Hiroaki , Kuwabara Hiroto , Léger Gabriel , Cumming Paul , Guttman Mark , Gjedde Albert
Published: April 2011

In 11 normal volunteers and six patients with Parkinson's disease, we compared six different analyses of dopaminergic function with l-3,4-dihydroxy-6-[18F]fluorophenylalanine (FDOPA) and positron emission tomography (PET). The caudate nucleus, putamen, and several reference regions were identified in PET images, using magnetic resonance imaging (MRI). The six analyses included two direct determinations of DOPA decarboxylase activity ( kD3, k*3), the slope–intercept plot based on plasma concentration ( K), two slope–intercept plots based on tissue content ( kr3, ks3), and the striato–occipital ratio [ R( T)]. For all analyses, the difference between two groups of subjects (normal volunteers and patients with Parkinson's disease) was larger in the putamen than in the caudate. For the caudate nucleus, the DOPA decarboxylase activity ( kD3, k*3), tissue slope–intercept plots ( kr3, ks3), and striato–occipital ratio [ R( T)] analyses significantly discriminated between the normal volunteers and the patients with Parkinson's disease ( p < 0.005) [with least significance for k*3 ( p < 0.05)], while the plasma slope–intercept plot ( K) failed to do so. For the putamen, the values for kD3, k*3, K, kr3, ks3 and R( T) of normal volunteers were significantly higher than those of patients ( p < 0.005) [with least significance for K ( p < 0.025)]. Linear correlations were significant between kD3 and ks3; kD3 and kr3; kD3 and R( T); and kD3 and k*3, in this order of significance. We found no correlation between kD3 and K values in the caudate nucleus.
Measurement of Benzodiazepine Receptor Number and Affinity in Humans Using Tracer Kinetic Modeling, Positron Emission Tomography, and [11C]Flumazenil
Authors: Price Julie C. , Mayberg Helen S. , Dannals Robert F. , Wilson Alan A. , Ravert Hayden T. , Sadzot Bernard , Rattner Zachary , Kimball Allyn , Feldman Marc A. , Frost J. James
Published: April 2011

Kinetic methods were used to obtain regional estimates of benzodiazepine receptor concentration ( Bmax) and equilibrium dissociation constant ( Kd) from high and low specific activity (SA) [11C]flumazenil ([11C] Ro 15-1788) positron emission tomography studies of five normal volunteers. The high and low SA data were simultaneously fit to linear and nonlinear three-compartment models, respectively. An additional inhibition study (pretreatment with 0.15 mg/kg of flumazenil) was performed on one of the volunteers, which resulted in an average gray matter K1/ k2 estimate of 0.68 ± 0.08 ml/ml (linear three-compartment model, nine brain regions). The free fraction of flumazenil in plasma ( f1) was determined for each study (high SA f1: 0.50 ± 0.03; low SA f1: 0.48 ± 0.05). The free fraction in brain ( f2) was calculated using the inhibition K1/ k2 ratio and each volunteer's mean f1 value ( f2 across volunteers = 0.72 ± 0.03 ml/ml). Three methods (Methods I–III) were examined. Method I determined five kinetic parameters simultaneously [ K1, k2, k3 (= kon f2 Bmax), k4, and kon f2/SA] with no a priori constraints. An average kon value of 0.030 ± 0.003 n M−1 min−1 was estimated for receptor-rich regions using Method I. In Methods II and III, the kon f2/SA parameter was specifically constrained using the Method I value of kon and the volunteer's values of f2 and low SA (Ci/μmol). Four parameters were determined simultaneously using Method II. In Method III, K1/ k2 was fixed to the inhibition value and only three parameters were estimated. Method I provided the most variable results and convergence problems for regions with low receptor binding. Method II provided results that were less variable but very similar to the Method I results, without convergence problems. However, the K1/ k2 ratios obtained by Method II ranged from 1.07 in the occipital cortex to 0.61 in the thalamus. Fixing the K1/ k2 ratio in Method III provided a method that was physiologically consistent with the fixed value of f2 and resulted in parameters with considerably lower variability. The average Bmax values obtained using Method III were 100 ± 25 n M in the occipital cortex, 64 ±18 n M in the cerebellum, and 38 ± 5.5 n M in the thalamus; the average Kd was 8.9 ± 1.0 n M (five brain regions).
Live Computerized Videomicroscopy of Cerebral Microvessels in Brain Slices
Authors: Sagher Oren , Zhang Xi-Qing , Szeto Wilson , Thai Quoc Anh , Jin Yongcheng , Kassell Neal F. , Lee Kevin S.
Published: April 2011

A model system for studying cerebral microvasculature is presented in which submerged in vitro brain slices are examined by computerized videomicroscopy. Brain slices are superfused continuously with artificial cerebrospinal fluid, while blood vessels are monitored using a transmission light microscope with water immersion objectives. The responses to well-characterized vasoactive compounds indicate that basic physiological characteristics are maintained in this preparation. This model system represents a simple and rapid technique for studying cerebrovascular responses under conditions in which vessels are surrounded by their normal cellular microenvironment. An additional advantage of this technique is the ability to perform simultaneous electrophysiological recordings in identified neurons. This will facilitate the study of interactions between neuronal and vascular elements and may help elucidate mechanisms underlying the local regulation of cerebral microvasculature.
Validation of Continuous Thermal Measurement of Cerebral Blood Flow by Arterial Pressure Change
Authors: Wei Datong , Shea Mary , Saidel Gerald M. , Jones Stephen C.
Published: April 2011

A thermal measurement system to monitor cerebral blood flow (CBF) continuously from the cortical surface is evaluated in vivo. It has a temperature resolution of better than 0.001°C (1 m°C) and can compensate for baseline temperature fluctuations in the brain tissue. A new approach has been developed to test the capability of monitoring dynamic CBF response. Transient CBF changes associated with changes in mean arterial blood pressure (MABP) caused by repeated bolus norepinephrine injections are used to examine the response of the measurement system in both the heated mode, sensitive to flow, and the unheated mode, sensitive only to temperature. Experiments on 13 rats demonstrate that changes in the MABP are closely correlated with those of temperature difference in the heated mode. Regression analysis shows a mean slope of 0.9 m°C/mm Hg in the heated mode, which is significantly different from zero (p < 0.002) and from the mean slope in the unheated mode (p < 0.002). This indicates that flow signal in the system output can be distinguished from the baseline thermal fluctuations. Thus, the system can be used to detect and study dynamic perfusion changes from the brain surface with minimal tissue damage. Furthermore, analysis of the data shows that the transient flow signal before autoregulation is linearly correlated with changes in MABP.
Measurement of Regional Cerebral Blood Flow with Positron Emission Tomography: A Comparison of [15O]Water to [11C]Butanol with Distributed-Parameter and Compartmental Models
Authors: Quarles Robert P. , Mintun Mark A. , Larson Kenneth B. , Markham Joanne , MacLeod Ann Mary , Raichle Marcus E.
Published: April 2011

To further our understanding of the best way to measure regional CBF with positron emission tomography (PET), we directly compared two candidate tracers ([15O]water and [11C]butanol, administered intravenously) and two popular implementations of the one-compartment (IC) model: the autoradiographic implementation representing a single PET measurement of tissue radioactivity over 1 min and a dynamic implementation representing a sequence of measurements of tissue radioactivity over 200 s. We also examined the feasibility of implementing a more realistic, and thus more complex, distributed-parameter (DP) model by assigning fixed values for all of its parameters other than CBF and tracer volume of distribution ( Vd), a requirement imposed by the low temporal resolution and statistical quality of PET data. The studies were performed in three normal adult human subjects during paired rest and visual stimulation. In each subject seven regions of interest (ROIs) were selected, one of which was the primary visual cortex. The corresponding ROI were anatomically equivalent in the three subjects. Regional CBF, Vd, tracer arrival delay, and dispersion were estimated for the dynamic data curves. A total of 252 parameter sets were estimated. With [11C]butanol both implementations of the IC model provided similar results ( r = 0.97). Flows estimated using the 1C models were lower (p < 0.01) with [15O]water than with [11C]butanol. In comparison with the IC model, the constrained version of the DP used in these studies performed inadequately, overestimating high flow and underestimating low flow with both tracers, possibly as the result of the necessity of assigning fixed values for all of its parameters other than CBF and Vd.
Imaging Ischemic Tissue at Risk of Infarction during Stroke
Authors: Di Rocco Richard J. , Kuczynski Bruce L. , Pirro John P. , Bauer Al , Linder Karen E. , Ramalingam Kondareddiar , Cyr John E. , Chan Yee Wai , Raju Natarajan , Narra Rama K. , Nowotnik David P. , Nunn Adrian D.
Published: April 2011

Autoradiograms obtained after middle cerebral artery occlusion (MCAO) in spontaneously hypertensive rats show that the 99mTc complex of a 2-nitroimidazole-derivatized propylene amine oxime (BMS-181321) is selectively retained in acutely ischemic brain before disruption of the blood-brain barrier (BBB), but not in the ischemic infarct. BMS-181321 is therefore a marker of ischemic tissue at risk of infarction and its uptake, unlike that of x-ray and magnetic resonance contrast agents, does not require disruption of the BBB. In keeping with this conclusion, we have found that the single-pass cerebral extraction fraction of BMS-181321 is 0.67 at normal rat whole-brain blood flow. Sequential single-photon emission computed tomographic images obtained from cats after MCAO show that the initial distribution of BMS-181321 approximates regional CBF and that selective retention subsequently produces a positive image within the ischemic territory. BMS-181321 is the first Tc complex able to indicate not only ischemia, but also ischemic tissue at risk of infarction. Use of this novel Tc complex to monitor biochemical events during ischemia may contribute to the clinical management of acute stroke.
Acceleration of HSP70 and HSC70 Heat Shock Gene Expression following Transient Ischemia in the Preconditioned Gerbil Hippocampus
Authors: Aoki M. , Abe K. , Kawagoe J. , Nakamura S. , Kogure K.
Published: April 2011

To evaluate the mechanism of tolerance to ischemia, inductions of heat shock protein (HSP) 70 and heat shock cognate protein (HSC) 70 mRNAs in gerbil hippocampus were compared with in situ hybridization between cases of a single 3.5-min period of forebrain ischemia and a 3.5-min period of ischemia 2 days after 2-min pretreatment with ischemia. Immunohistochemistry for HSP70 protein and morphological studies were also performed in the same brains up to 7 days after the reperfusion. Following a single 3.5-min period of ischemia, HSP70 and HSC70 mRNAs were induced in all hippocampal cells. However, the hippocampal CA1 cells produced only a minimum of HSP70 protein, and the cells were almost lost by 7 days. Following 3.5 min of ischemia after 2-min pretreatment, large populations of the CA1 cells survived at 7 days. The peak time of the HSP70 and HSC70 mRNA induction shifted to an earlier period of reperfusion in all hippocampal cells as compared with the case of a single episode of ischemia. The peak of HSP70 and HSC70 mRNA induction shifted from 1 day to 3 h in the CA1 cells. The CA1 cells produced strongly immunoreactive HSP70 from 3 hr to 2 days. These results suggest that pretreatment with an initial period of ischemia (for 2 min) accelerated HSP70 and HSC70 gene expression at the transcriptional level, ameliorated the translational disturbance of HSP70 mRNA to protein, and saved the CA1 cells from subsequent lethal ischemia (for 3.5 min). These changes of heat shock gene expression might play important roles in the acquisition of ischemic tolerance of hippocampal CA1 neurons.
Induction of c-Fos, junB, c-Jun, and hsp70 mRNA in Cortex, Thalamus, Basal Ganglia, and Hippocampus following Middle Cerebral Artery Occlusion
Authors: Kinouchi Hiroyuki , Sharp Frank R. , Chan Pak H. , Koistinaho Jari , Sagar Stephen M. , Yoshimoto Takashi
Published: April 2011

Middle cerebral artery (MCA) occlusion in halothane-anesthetized rats induced c-fos, junB, and c-jun immediate early gene mRNAs and hsp70 heat shock gene mRNA in brain. In situ hybridization studies showed that c-fos and junB were induced throughout all of the cortex at 1 and 4 h following MCA occlusion. hsp70 was induced in the core and margins of the MCA ischemia. By 24 h, there was little expression of c-fos, junB, c-jun, and hsp70 in the core of the MCA infarct; there was modest induction of hsp70 at the margins of the infarct; and there was diffuse induction of c-fos, junB, and c-jun in all of the cortex outside the infarct. MCA occlusion also induced these genes in subcortical structures. c-fos, junB, and hsp70 were induced in ipsilateral medial striatum, most of thalamus including medial and lateral geniculate nuclei, substantia nigra, and hippocampus. Most of these structures, except for the striatum, are not supplied by the MCA. These data show that changes in gene expression can occur in regions remote from an infarction.
Ischemia Induces the Expression of the Platelet-Derived Growth Factor-B Chain in Neurons and Brain Macrophages in vivo
Authors: Iihara Koji , Sasahara Masakiyo , Hashimoto Nobuo , Uemura Yoshihiko , Kikuchi Haruhiko , Hazama Fumitada
Published: April 2011

To elucidate the role of the platelet-derived growth factor (PDGF)–B chain in the brain, we examined its expression in rat brains with focal ischemia. Focal ischemia was induced by permanent tandem occlusion of the middle cerebral and common carotid arteries in spontaneously hypertensive rats (SHRs). Northern analysis demonstrated that ischemia transiently increased mRNA expression of the PDGF–B chain, but not the PDGF–A chain, in the injured neocortex. The larger transcript (3.5 kb) of the B chain gradually increased to threefold by 16 h, whereas the smaller transcript (2.6 kb) of the B chain markedly increased sixfold by 4 h. Immunohistochemistry revealed enhanced immunoreactivity in the neurons in the infarct and in the periinfarct area from 16 h to days 4–7, with a peak at 24 h. Furthermore, the brain macrophages that accumulated in the infarct showed intense immunostaining in their perinuclear region from days 2 to 14, with a peak at days 5–6. The present study demonstrates that ischemia induces the expression of the PDGF–B chain, first in neurons and later in brain macrophages, and suggests an important role of the PDGF–B chain in the healing process of the injured brain.
Microglial Response to Transient Focal Cerebral Ischemia: An Immunocytochemical Study on the Rat Cerebral Cortex Using Anti-Phosphotyrosine Antibody
Authors: Korematsu Kojiro , Goto Satoshi , Nagahiro Shinji , Ushio Yukitaka
Published: April 2011

Microglial response to transient focal ischemia was examined using an immunohistochemical method with a monoclonal antibody to phosphotyrosine (P-Tyr). For this purpose, a rat model of reversible middle cerebral artery occlusion for 1 h was used. Compared with results in the noninsulted hemisphere, there was a significant increase in P-Tyr immunolabeling of the microglia in the insulted cerebral cortex 3 h postreperfusion. This microglial reaction progressed up to 24 h after ischemic insult. In the affected cerebral cortex, morphological changes of the microglia positive for P-Tyr were also observed, with shortened and thickened processes, enlarged cell bodies, and ameboid features. Cell density analysis did not show any apparent change in number of P-Tyr–positive microglia in the insulted cortex at 6, 12, and 24 h after reperfusion, suggesting that the cells with increased P-Tyr immunoreactivity were resident microglia. The present findings suggest that signal transduction mediated by tyrosine phosphorylation is involved in the microglial response to ischemic injury in the rat cerebral cortex.
Dissociation of Adenosine Levels from Bioenergetic State in Experimental Brain Trauma: Potential Role in Secondary Injury
Authors: Headrick John P. , Bendall M. Robin , Faden Alan I. , Vink Robert
Published: April 2011

Intracellular bioenergetic state and extracellular adenosine levels were monitored in rat brain prior to and following traumatic brain injury (TBI) using phosphorus magnetic resonance spectroscopy and microdialysis, respectively. Fluid percussion-induced TBI (2.6 ± 0.2 atm) resulted in significant reductions in free cytosolic [Mg2+], cytosolic [ATP]/[ADP][Pi], and Δ GATP and elevations in cytosolic [ADP] and [5'-AMP]. Intracellular ATP concentration and pH did not change significantly after trauma. Mitochondrial capacity for oxidative phosphorylation (indexed by V/Vmax) increased significantly from ∼0.45 prior to injury to ∼0.58 following TBI. All metabolic changes were maximal at 2–3 h post-TBI. Conversely, extracellular adenosine concentrations increased transiently following TBI, with levels peaking at 10 min posttrauma, then declining rapidly to preinjury values by 50 min. Thus, despite pronounced long-term depression in bioenergetic status and a marked rise in [5'-AMP], formation and release of adenosine were elevated only transiently within the first hour following TBI. Since steady-state adenosine levels were essentially unchanged beyond 1 h posttrauma, mooted neuroprotective actions of endogenous adenosine would be minimized. Intracerebro-ventricular injections of 2-chloroadenosine (0.5 and 2.5 nmol) immediately prior to TBI dose-dependently attenuated metabolic disturbances and improved posttraumatic neurologic outcome (p < 0.05). The observations indicate that (a) TBI results in dissociation of adenosine release from intracellular bioenergetic state, a phenomenon possibly contributing to secondary injury following TBI; and (b) supplementing brain with an adenosine agonist attenuates irreversible injury.
Attenuation of p53 Expression Protects against Focal Ischemic Damage in Transgenic Mice
Authors: Crumrine R. Christian , Thomas Amy L. , Morgan Philip F.
Published: April 2011

Apoptosis or programmed cell death may be involved in neuronal death in the cerebral cortex after a permanent focal ischemic insult. Studies indicate that protein p53 is a major determinant of the cellular mechanism that leads to programmed cell death. Wild-type C57 mice and two groups of transgenic C57 mice, one homozygous and the other heterozygous for a p53 null gene, were subjected to middle cerebral artery occlusion. As expected, the wild-type mice had a large, consistent infarct volume (22.11 ± 4.59 mm3; n = 10). Both transgenic groups had significantly less ischemic damage than the wild-type control group. However, unexpectedly, the heterozygous group had the least amount of ischemic damage (16.12 ± 1.71 mm3, n = 11; 27% reduction in infarct size). The ischemic damage in the homozygous group (18.72 ± 3.48 mm3, n = 9) was significantly less than in the wild-type control (15% reduction in infarct size) but significantly more than in the heterozygous group. Thus, although the absence of p53 expression was protective, grater protection was afforded by reduced expression of p53. These data suggest that attenuated p53 expression may be protective after an ischemic event.
Brain Metabolism during Short-Term Starvation in Humans
Authors: Hasselbalch Steen G. , Knudsen Gitte M. , Jakobsen Johannes , Hageman Lars Pinborg , Holm Søren , Paulson Olaf B.
Published: April 2011

During prolonged starvation, brain energy requirements are covered in part by the metabolism of ketone bodies. It is unknown whether short-term starvation of a few days' duration may lead to reduced brain glucose metabolism due to the change toward ketone body consumption. In the present study we measured the cerebral metabolism of glucose and ketone bodies in nine healthy volunteers before and after 3.5 days of starvation. Regional glucose metabolism was measured by dynamic positron emission tomography using [18F]2-fluoro-2-deoxy-D-glucose. The mean value of K*1 in gray and white matter increased by 12% (p < 0.05), whereas k*2 and k*3 were unchanged compared with control values. Regional glucose metabolism in cortical gray matter was reduced by 26% from 0.294 ± 0.054 to 0.217 ± 0.040 μmol g−1 min−1 (p < 0.001). White matter glucose metabolism decreased by 27% (p < 0.02). The decrease was uniform in gray and white matter with regional decreases ranging from 24 to 30%. A determination using Fick's principle confirmed the reduction in glucose metabolism yielding a decrease of 24% from 0.307 ± 0.050 to 0.233 ± 0.073 μmol g−1 min−1 (p < 0.05), whereas CBF did not change (0.57 ± 0.07 vs. 0.57 ± 0.06 ml g−1 min−1). The global net uptake of β-hydroxybutyrate increased 13-fold from 0.012 ± 0.024 to 0.155 ± 0.140 μmol g−1 min−1 (p < 0.05). Net uptake of acetoacetate and net efflux of lactate and pyruvate did not change significantly during starvation. The present study shows that the human brain adapts to the changes in energy supply as early as 3 days following initiation of starvation, at which time ketone bodies account for approximately one-fourth of the cerebral energy requirements.
Magnetic Resonance Imaging of Propagating Waves of Spreading Depression in the Anaesthetised Rat
Authors: Gardner-Medwin A. R. , van Bruggen N. , Williams S. R. , Ahier R. G.
Published: April 2011

Gradient echo magnetic resonance (MR) imaging was used to demonstrate propagating waves of cortical spreading depression (SD) in the anaesthetised rat. SD was initiated by remote perfusion with 150 m M KCl applied for 0.5–2 min to the left parietal cortex. Gradient echo MR images were obtained every 12–30 s in either a vertical coronal section or a horizontal section including the superficial cortex in plan view. Within 2 min of application of KCl, we observed a zone of increased signal intensity (3–15%) on the MR image, up to 2 mm across, lasting approximately 1 min and propagating away from the site of initiation. The mean velocity for 27 of such waves seen in seven animals was calculated to be 2.79 mm/min, with means (±SD) in individual animals averaging 2.90 ± 0.46 mm/min (n = 7). Increased signal intensity in gradient echo images has been attributed to an increased level of oxygenation within the venous blood. Our results are consistent with this interpretation although other physiological changes during SD may also contribute to the signal changes.
Prostaglandin E1 Induces c-Fos and Myc Proteins and Protects Rat Hippocampal Cells against Hypoxic Injury
Authors: Otsuki Hideo , Yamada Kazuo , Yuguchi Takamichi , Taneda Mamoru , Hayakawa Toru
Published: April 2011

We investigated the effects of prostaglandin (PG) E1 on the hypoxic injury of fetal rat hippocampal cells. Primary hippocampal cell cultures (embryonic day 18) were established and maintained. After 72 h in culture, PGE1 was added to the serum-free medium at a final concentration of 10−5-10−9 M. Cultures were divided into two groups: The normoxia group was in culture for another 48 h, and the hypoxia group was exposed to 24 h of hypoxia followed by continuation of culture for another 24 h. As a quantitative measure of cell death, lactate dehydrogenase (LDH) activity was estimated in the culture medium. The LDH activity, released by the hypoxic insult, was significantly smaller with PGE1 treatment at 10−6, 10−7, and 10−8 M (p < 0.01) and 10−9 M (p < 0.05) compared with the control. No differences in the LDH activities were observed in the normoxia group. Glial culture was not affected by the hypoxia. Western blot analysis showed an increased induction of 62-kDa c-Fos and 58, 60, and 66 kDa Myc proteins in rat hippocampal cells with 10−7 M PGE1 treatment. We conclude that PGE1 at concentrations of 10−6-10−9 M protects rat hippocampal neurons against hypoxic insult.