bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitation of rCBF by 99mTc-Hexamethylpropyleneamine Oxime Single Photon Emission Computed Tomography Combined with 133Xe CBF
Authors: Isaka Yoshinari , Itoi Yoshihito , Imaizumi Masatoshi , Ashida Keiichi , Okamoto Masaya , Iiji Osamu
Published: April 2011

A simple, noninvasive method of measuring CBF that uses single photon emission computed tomography (SPECT) of 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) and whole-brain CBF obtained by 133Xe clearance technique was developed. SPECT data were normalized to the count density of HMPAO uptake in the whole brain and then converted to the absolute units of CBF by multiplying average CBF in the whole brain obtained by 133Xe. Mean CBF values in healthy volunteers (n = 12) were 49 ± 7 and 30 ± 5 ml 100 g−1 min−1 for gray matter and white matter, respectively, with a global flow value of 45 ± 5 ml 100 g−1 min−1. The mean flow value was 19 ± 7 ml 100g−1 min−1 for the core of the infarct and 31 ± 5 ml 100 g−1 min−1 for the contralateral region (n = 13). CBF values were reproducible for all brain regions. The method was convenient to use and suitable for the routine measurement of regional CBF in normal and pathologic states.
Blood—Brain Barrier Permeability and Brain Concentration of Sodium, Potassium, and Chloride during Focal Ischemia
Authors: Betz A. Lorris , Keep Richard F. , Beer Mary E. , Ren Xiao-Dan
Published: April 2011

Brain edema formation during the early stages of focal cerebral ischemia is associated with an increase in both sodium content and blood–brain barrier (BBB) sodium transport. The goals of this study were to determine whether chloride is the principal anion that accumulates in ischemic brain, how the rate of BBB transport of chloride compares with its rate of accumulation, and whether the stimulation seen in BBB sodium transport is also seen with other cations. Focal ischemia was produced by occlusion of the middle cerebral artery (MCAO) in anesthetized rats. Over the first 6 h after MCAO, the amount of brain water in the center of the ischemic cortex increased progressively at a rate of 0.15 ± 0.02 (SE) g/g dry wt/h. This was accompanied by a net increase in brain sodium (48 ± 12 μmol/g dry wt/h) and a loss of potassium (34 ± 7 μmol/g dry wt/h). The net rate of chloride accumulation (16 ± 1 μmol/g dry wt/h) approximated the net rate of increase of cations. Three hours after MCAO, the BBB permeability to three ions (22Na, 36Cl, and 86Rb) and two passive permeability tracers {[3H]α-aminoisobutyric acid (3H]AIB) and [14C]urea} was determined. Permeability to either passive tracer was not increased, indicating that the BBB was intact. The rate of 36Cl influx was 3 times greater and the rate of 22Na influx 1.8 times greater than their respective net rates of accumulation in ischemic brain. The BBB permeability to 22Na relative to that of [3H]AIB was significantly increased in the ischemic cortex, the relative permeability to 86Rb was significantly decreased, and the relative permeability to 36Cl was unchanged. These results indicate that the stimulation in BBB sodium transport is specific for sodium. Further, chloride accumulates with sodium in brain during the early stages of ischemia; however, its rate of accumulation is low compared with its rate of transport from blood to brain. Therefore, inhibition of BBB sodium transport is more likely to reduce edema formation than is inhibition of BBB chloride transport.

This study demonstrates that chloride is the principal anion that accompanies the accumulation of sodium in ischemic brain, but its rate of accumulation in brain is much less than its rate of movement into brain, and therefore inhibition of chloride uptake would have little effect on brain edema formation. There is a specific acceleration of blood-to-brain sodium transport during ischemia that is not seen with another positively charged ion, 86Rb. This is consistent with stimulation of brain capillary Na,K-ATPase activity in response to the elevated extracellular potassium concentration. Inhibition of potassium influx across the BBB would probably be more successful in lessening edema formation than accelerating potassium efflux. However, inhibition of blood-to-brain sodium transport is likely to be a more effective approach to reducing brain edema formation during the early stages of cerebral ischemia.
The Use of Spectral Analysis to Determine Regional Cerebral Glucose Utilization with Positron Emission Tomography and [18F]Fluorodeoxyglucose: Theory, Implementation, and Optimization Procedures
Authors: Turkheimer F. , Moresco R. M. , Lucignani G. , Sokoloff L. , Fazio F. , Schmidt K.
Published: April 2011

A method for kinetic analysis of dynamic positron emission tomography (PET) data by linear programming that allows identification of the components of a measured PET signal without predefining a compartmental model has recently been proposed by Cunningham and co-workers. The method identifies a small subset of functions from a large input set of feasible functions that best fits the time course of total radioactivity measured by PET. To investigate in detail the properties of this technique, we applied it to PET studies with [18F]fluorodeoxyglucose, a tracer with well-characterized kinetic properties. We examined dynamically acquired data over various time intervals in many brain regions and found that the number of components identified by the method is stable and consistent with the presence of kinetic heterogeneity in every region. We optimized the method for determination of regional rates of glucose utilization; calculated rates were found to be somewhat dependent upon the treatment of noise in the measured tissue data and upon the time interval in which the data were collected. The application of a numerical filter to remove noise in the data resulted in values for regional cerebral glucose utilization that were stable with time and consistent with rates determined by the other established techniques. Based on the results of the current study, we expect that the spectral analysis technique will prove to be a highly flexible tool for kinetic analysis of other tracer compounds; it is capable of producing low-variance, time-stable estimates of physiological parameters when optimized for time interval of application, input spectrum of components, and processing of noise in the data.
Angiotensin II AT2 Receptor Stimulation Extends the Upper Limit of Cerebral Blood Flow Autoregulation: Agonist Effects of CGP 42112 and PD 123319
Authors: Näveri Liisa , Strömberg Christer , Saavedra Juan M.
Published: April 2011

The effects of the angiotensin II AT2 receptor ligands CGP 42112 and PD 123319, the AT1 antagonist losartan, and the nonselective angiotensin II antagonist Sar1,Ile8-angiotensin II on the upper limit of CBF autoregulation were studied in pentobarbital-anesthetized rats. Blood pressure was increased by intravenous phenylephrine infusion, while CBF was measured continuously from the parietal cortex by laser–Doppler flowmetry. Intravenous infusions of CGP 42112 (0.1 and 1 mg kg−1 min−1) and PD 123319 (0.36 and 1 mg kg−1 min−1) shifted the upper limit of CBF autoregulation toward higher blood pressures without affecting baseline CBF. Sar1,Ile8-angiotensin II (4 μg kg−1 min−1) had no effect on baseline CBF or CBF autoregulation but antagonized the effect of CGP 42112 and PD 123319. Losartan (10 mg/kg i.v. bolus) reduced baseline blood pressure and CBF and shifted the autoregulation curve toward higher blood pressures. Sar1,Ile8-angiotensin II blocked the effect of losartan on baseline CBF but not on CBF autoregulation. These results suggest that both CGP 42112 and PD 123319 exert their effects on CBF autoregulation through stimulation of angiotensin II AT2 receptors. The mechanism by which losartan affects CBF remains unclear.
Cerebral Pressure-Flow Relationship during Cardiopulmonary Bypass in the Dog at Normothermia and Moderate Hypothermia
Authors: Mutch W. A. C. , Sutton I. R. , Teskey J. M. , Cheang M. S. , Thomson I. R.
Published: April 2011

We studied cerebral autoregulation by analyzing cerebral pressure–flow curves during cardiopulmonary bypass (CPB) with alpha-stat (α-stat) acid–base management at 28 ( n = 9) and 37°C ( n = 9) in two groups of dogs. Cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) were determined multiple times in each animal over an extensive range of cerebral perfusion pressure (CPP). The CPP was altered by changing perfusion flow rate. The dependence of CBF on CPP during normothermic and moderate hypothermic CPB was assessed using a block design analysis of covariance with CPP as the covariate. We anticipated maximal statistical power with this analysis to define if cerebral autoregulation was intact. This method of statistical analysis was compared with the conventional interpretation by linear regression analysis. Animals were administered sodium thiopental until an isoelectric electroencephalogram was obtained to assure stable depth of anesthesia independently of temperature effects. The animals were randomly assigned to either temperature group. The CBF was determined by injection of radioactive microspheres at each of five target CPPs randomly allocated (50, 60, 70, 80, and 90 mm Hg). The brain oxygen content difference was defined as arterial minus superior sagittal sinus (SSS) oxygen content. No difference in CPP, hemoglobin, arterial carbon dioxide tension, or pH was seen between groups at any time period. In both groups, total CBF (tCBF) increased significantly with increasing CPP ( p = 0.012 and 0.017 for normothermic and hypothermic CPB, respectively; CPP as covariate). The between-group difference in slopes (CPP × temperature effect) approached statistical significance ( p = 0.059). For cerebral hemispheric CBF (hCBF), autoregulation was also impaired ( p = 0.007 and 0.015, respectively). There was a significant between-group difference in slopes with a steeper slope for normothermia ( p = 0.032). An inverse relation for arterial minus SSS oxygen content versus CPP was found ( p = 0.0001 for both groups). The Q10 (the ratio of cerebral metabolic rates for oxygen for a 10°C change in temperature) was 3.8. In this study, using a block design analysis of covariance, tCBF was dependent on CPP during normothermia and moderate hypothermia with deep barbiturate anesthesia. We conclude that during CPB with α-stat acid–base management, the autoregulatory plateau was not horizontal for either temperature. In addition, for supratentorial structures (cerebral hemispheres), autoregulation was significantly more impaired for normothermia than for moderate hypothermia.
Reduction of Focal Cerebral Ischemic Damage by Delayed Treatment with Nitric Oxide Donors
Authors: Zhang Fangyi , Iadecola Costantino
Published: April 2011

We studied whether delayed posttreatment with the nitric oxide donor 3-morpholinosydnonimine (SIN-1) is effective in reducing the size of the infarct produced by occlusion of the middle cerebral artery (MCA) in spontaneously hypertensive rats (SHRs). SHRs were anesthetized with halothane and intubated transorally. The left MCA was occluded at the level of the inferior cerebral vein. Cerebral blood flow (CBF) was monitored in the ischemic hemisphere by a laser-Doppler flowmeter, and an electroencephalogram (EEG) was recorded. SIN-1 was infused into the left internal carotid artery for 60 min starting 3, 15, 30, 60 or 120 min after MCA occlusion. The hypotension associated with SIN-1 administration was controlled by i.v. administration of phenylephrine. At the end of the infusion, rats were extubated and allowed to recover. Infarct size was measured 24 h later on thionin-stained coronal brain sections by computer-assisted planimetry. SIN-1 infusion 3 min after MCA occlusion enhanced the recovery of CBF and EEG amplitude and reduced the size of the infarct by 30 ± 11% (p < 0.05, analysis of variance). The reduction in infarct size by SIN-1 was still seen when SIN-1 was administered 15, 30, and 60 min after MCA occlusion (p < 0.05). However, administration of SIN-1 2 h after MCA occlusion did not affect the size of the infarct (p > 0.05). We conclude that posttreatment with SIN-1 is effective in reducing focal ischemic damage if this agent is administered up to 60 min after MCA occlusion. Thus, NO donors, alone or in combination with other treatment modalities, may have therapeutic potential in the management of acute ischemic stroke.
Major Role of Nitric Oxide in the Mediation of Regional CO2 Responsiveness of the Cerebral and Spinal Cord Vessels of the Cat
Authors: Sandor P. , Komjati K. , Reivich M. , Nyary I.
Published: April 2011

The role of nitric oxide (NO) in the mediation of cerebrovascular CO2 responsiveness was studied in 10 distinct brain and spinal cord regions of the anesthetized, ventilated, temperature-controlled, normoxic cat. Regional CBF was measured with 15-μm radiolabeled microspheres in hypocapnic, normocapnic, and hypercapnic conditions. CO2 responsiveness of each region was determined from the equation of the best-fit regression lines to the obtained flow values. The effect of altered endothelial and/or neuronal NO synthesis on CO2 responsiveness was studied following either selective blockade of the NO synthase enzyme by Nω-nitro-L-arginine methyl ester (L-NAME; 3 or 30 mg/kg i.v.) or simultaneous administration of L-NAME (3 mg/kg i.v.) and a large dose of the NO precursor L-arginine (30 mg/kg i.v.). Blockade of NO synthesis by 30 mg/kg L-NAME resulted in a significant reduction of the steady-state regional blood flow values and in an almost complete abolition of the CO2 sensitivity in each region studied. Changes of the basal flow values as well as the reduction of the regional CO2 sensitivity were dose dependent. Hypothalamic, sensorimotor cortical, and cerebellar regions were the areas most sensitive to the NO blockade. Impaired CO2 responsiveness following NO synthase inhibition, however, was reversed in these regions by simultaneous administration of a large dose of intravenously injected L-arginine. These findings suggest a major role of nitric oxide in the mediation of regional cerebrovascular CO2 responsiveness in cats.
The Brain at High Altitude: Hypometabolism as a Defense against Chronic Hypoxia?
Authors: Hochachka P. W. , Clark C. M. , Brown W. D. , Stanley C. , Stone C. K. , Nickles R. J. , Zhu G. G. , Allen P. S. , Holden J. E.
Published: April 2011

The brain of hypoxia-tolerant vertebrates is known to survive extreme limitations of oxygen in part because of very low rates of energy production and utilization. To assess if similar adaptations may be involved in humans during hypoxia adaptation over generational time, volunteer Quechua natives, indigenous to the high Andes between about 3,700 and 4,900 m altitude, served as subjects in positron emission tomographic measurements of brain regional glucose metabolic rates. Two metabolic states were analyzed: (a) the presumed normal (high altitude-adapted) state monitored as soon as possible after leaving the Andes and (b) the deacclimated state monitored after 3 weeks at low altitudes. Proton nuclear magnetic resonance spectroscopy studies of the Quechua brain found normal spectra, with no indication of any unusual lactate accumulation; in contrast, in hypoxia-tolerant species, a relatively large fraction of the glucose taken up by the brain is released as lactate. Positron emission tomographic measurements of [18F]2-deoxy-2-fluoro-d-glucose (FDG) uptake rates, quantified in 26 regions of the brain, indicated systematically lower region-by-region glucose metabolic rates in Quechuas than in lowlanders. The metabolic reductions were least pronounced in primitive brain structures (e.g., cerebellum) and most pronounced in regions classically associated with higher cortical functions (e.g., frontal cortex). These differences between Quechuas with lifetime exposure to hypobaric hypoxia and lowlanders, which seem to be expressed to some degree in most brain regions examined, may be the result of a defense adaptation against chronic hypoxia.
Preservation of Cerebral Blood Flow Responses to Hypoxia and Arterial Pressure Alterations in Hyperammonemic Rats
Authors: Hirata Takahiko , Koehler Raymond C. , Brusilow Saul W. , Traystman Richard J.
Published: April 2011

Acute hyperammonemia causes cerebral edema, elevated intracranial pressure and loss of cerebral blood flow (CBF) responsivity to CO2. Inhibition of glutamine synthetase prevents these abnormalities. If the loss of CO2 responsivity is secondary to the mechanical effects of edema, one would anticipate loss of responsivity to other physiological stimuli, such as hypoxia and changes in mean arterial blood pressure (MABP). To test this possibility, pentobarbital-anesthetized rats were subjected to either hypoxic hypoxia (Pao2 ≈ 30 mm Hg), hemorrhagic hypotension (MABP ≈70 and 50 mm Hg), or phenylephrine-induced hypertension (MABP ≈ 125 and 145 mm Hg). CBF was measured with radiolabeled microspheres. Experimental groups received intravenous ammonium acetate (≈50 μmol min−1 kg−1) for 6 h to increase plasma ammonia to 500–600 μM. Control groups received sodium acetate plus HCl to prevent metabolic alkalosis. The increase in CBF during 10 min of hypoxia after 6 h of ammonium acetate infusion (84 ± 19 to 259 ± 52 ml min−1 100 g−1) was similar to that after sodium acetate infusion (105 ± 20 to 265 ± 76 ml min−1 100 g−1). Cortical glutamine concentration was elevated equivalently in hyperammonemic rats subjected to normoxia only or to 10 min of hypoxia. With severe hypotension, CBF was unchanged in both the ammonium (80 ± 20 to 76 ± 24 ml min−1 100 g−1) and the sodium (80 ± 14 to 73 ± 16 ml min−1 100 g−1) acetate groups. With moderate hypertension, CBF was unchanged. With the most severe hypertension, significant increases in CBF occurred in both groups, but there was no difference between groups. We conclude that hypoxic and autoregulatory responses are intact during acute hyperammonemia. The previously observed loss of CO2 responsivity is not the result of a generalized vasoparalysis to all physiological stimuli.
Nitric Oxide Modulates the CBF Response to Increased Extracellular Potassium
Authors: Dreier J. P. , Körner K. , Görner A. , Lindauer U. , Weih M. , Villringer A. , Dirnagl U.
Published: April 2011

The response of the regional cerebral blood flow (rCBF) to brain topical superfusion of 20 m M K+ was characterized in a closed cranial window preparation in barbiturate anesthetized and ventilated rats; Increasing K+ in the artificial cerebrospinal fluid (ACSF) induced a rCBF elevation (measured by laser–Doppler flowmetry) of +85 ± 37% above baseline (n = 19). This elevation was stable for >3 h with continuous superfusion of increased K+ (n = 5) and partially reversible to a level of + 18 ± 19% above baseline when returning to a physiological K+ concentration. Nitric oxide synthase (NOS) inhibition by brain topical superfusion with Nω-nitro-L-arginine (L-NA) revealed (a) Addition of L-NA to high-potassium ACSF reduced the rCBF increase from + 94 ± 36% to + 21 ± 18% (p ≤ 0.01, n = 7). (b) When L-NA was superfused for 60 min before increasing K+, rCBF decreased to – 17 ± 7% below baseline. Subsequent coapplication of L-NA and increased K+ induced only an elevation of +7 ± 4% above baseline (n = 4). (c) When the NO donor S-nitroso- N-acetylpenicillamine (SNAP) was added during NOS inhibition to restore basal tissue NO levels, the resultant level of rCBF was +28 ± 54% above baseline. Subsequent increase of K+ in the presence of NOS inhibition and SNAP elevated rCBF to + 137 ± 89% above baseline (n = 4). Statistical analysis comparing K+-induced elevation of rCBF (a) without any added drugs, (b) in the presence of NOS inhibition with L-NA, and (c) in the presence of both NOS inhibition and SNAP revealed that K+-induced elevation in the presence of NOS inhibition was significantly reduced (p ≤ 0.05) whereas no statistical difference was found between K+-induced elevation of rCBF without drugs compared with the K+-induced elevation of rCBF in the presence of L-NA and SNAP. We conclude that NO is a modulator of the rCBF elevation to increased extracellular K+ concentration.
Evolution of Regional Changes in Apparent Diffusion Coefficient during Focal Ischemia of Rat Brain: The Relationship of Quantitative Diffusion NMR Imaging to Reduction in Cerebral Blood Flow and Metabolic Disturbances
Authors: Hoehn-Berlage Mathias , Norris David G. , Kohno Kanehisa , Mies Günter , Leibfritz Dieter , Hossmann Konstantin-Alexander
Published: April 2011

Middle cerebral artery occlusion was performed in rats while the animals were inside the nuclear magnetic resonance (NMR) tomograph. Successful occlusion was confirmed by the collapse of amplitude on an electrocorticogram. The ultrafast NMR imaging technique UFLARE was used to measure the apparent diffusion coefficient (ADC) immediately after the induction of cerebral ischemia. ADC values of normal cortex and caudate-putamen were 726 ± 22 × 10−6 mm2/s and 659 ± 17 × 10−6 mm2/s, respectively. Within minutes of occlusion, a large territory with reduced ADC became visible in the ipsilateral hemisphere. Over the 2 h observation period, this area grew continuously. Quantitative analysis of the ADC reduction in this region showed a gradual ADC decrease from the periphery to the core, the lowest ADC value amounting to about 60% of control. Two hours after the onset of occlusion, the regional distribution of ATP and tissue pH were determined with bioluminescence and fluorescence techniques, respectively. There was a depletion of ATP in the core of the ischemic territory (32 ± 20% of the hemisphere) and an area of tissue acidosis (57 ± 19% of the hemisphere) spreading beyond that of ATP depletion. Regional CBF (rCBF) was measured autoradiographically with the iodo[14C]antipyrine method. CBF gradually decreased from the periphery to the ischemic core, where it declined to values as low as 5 ml 100 g−1 min−1. When reductions in CBF and in ADC were matched to the corresponding areas of energy breakdown and of tissue acidosis, the region of energy depletion corresponded to a threshold in rCBF of 18 ± 14 ml 100 g−1 min−1 and to an ADC reduction to 77 ± 3% of control. Tissue acidosis corresponded to a flow value below 31 ± 11 ml 100 g−1 min−1 and to an ADC value below 90 ± 4% of control. Thus, the quantification of ADC in the ischemic territory allows the distinction between a core region with total breakdown of energy metabolism and a corona with normal energy balance but severe tissue acidosis.
Outcome Model of Asphyxial Cardiac Arrest in Rats
Authors: Katz Laurence , Ebmeyer Uwe , Safar Peter , Radovsky Ann , Neumar Robert
Published: April 2011

An outcome model with asphyxial cardiac arrest in rats has been developed for quantifying brain damage. Twenty-two rats were randomized into three groups. Control group I was normal, was conscious, and had no asphyxia ( n = 6). Sham group II had anesthesia and surgery but no asphyxia ( n = 6). All 12 rats in groups I and II survived to 72 h and were functionally and histologically normal. Arrest group III (the model; n = 10) had light anesthesia and apneic asphyxia of 8 min, which led to cessation of circulation at 3–4 min of apnea, resulting in cardiac arrest (no flow) of 4–5 min. All 10 rats had spontaneous circulation restored by standard external cardiopulmonary resuscitation. Nine rats survived controlled ventilation for 1 h and observation to 72 h, while one rat died before extubation. All nine survivors were conscious at 72 h, with neurologic deficit scores (0% = best; 100% = worst) of 7 ± 69? (2–16%). All brain regions at five coronal levels were examined for ischemic neurons. The prevalence of ischemic neurons in five regions was categorically scored. The average total brain histopathologic damage score in group III ( n = 9) was 2.1 ( p < 0.05 vs. group I or II). A reproducible outcome model of cardiac arrest in rats was documented. It provides a tool for investigating pathophysiological mechanisms of neuronal death caused by a transient global hypoxic–ischemic brain insult.
Metabolic Response to Tacrine (THA) and Physostigmine in the Aged Rat Brain
Authors: Bassant M. H. , Jazat-Poindessous F. , Lamour Y.
Published: April 2011

The effects of the centrally acting anticholinesterases tacrine (tetrahydroaminoacridine, THA) and physostigmine (PHY), on local cerebral glucose utilization (LCGU) have been studied in 27-month-old rats, using the autoradiographic [14C]deoxyglucose technique. THA (10 mg/kg i.p.) increased LCGU significantly in 13 of the 54 regions studied (24%) including insular, parietal, temporal, and retrosplenial cortices, septohippocampal system, thalamus, lateral habenula, and superior colliculus. In these regions, the average THA-induced increase in LCGU was 24% above control. The whole brain mean LCGU was not significantly increased. PHY (0.5 mg/kg) increased LCGU in 18% of the regions (average elevation, 23%). The whole brain mean LCGU increased by 7% ( p < 0.05). The regional distributions of THA- and PHY-induced increases in LCGU were extremely similar and overlapped the distribution of the M2 muscarinic receptors and that of acetylcholinesterase activity, suggesting that the major effects of THA and PHY on LCGU result from their anticholinesterase action. As compared to those of 3-month-old rats, both the number of regions affected and the amplitude of the metabolic activation were significantly less in aged rats. However, the drugs were still active in old rats and compensated for the age-related hypometabolism in some brain areas.
Regional Differences in Late-Onset Iron Deposition, Ferritin, Transferrin, Astrocyte Proliferation, and Microglial Activation after Transient Forebrain Ischemia in Rat Brain
Authors: Kondo Yoichi , Ogawa Norio , Asanuma Masato , Ota Zensuke , Mori Akitane
Published: April 2011

With use of iron histochemistry and immuno-histochemistry, regional changes in the appearance of iron, ferritin, transferrin, glial fibrillary acidic protein–positive astrocytes, and activated microglia were examined from 1 to 24 weeks after transient forebrain ischemia (four-vessel occlusion model) in rat brain. Expression of the C3bi receptor and the major histocompatibility complex class II antigen was used to identify microglia. Neuronal death was confirmed by hematoxylin–eosin staining only in pyramidal cells of the hippocampal CA, region, which is known as the area most vulnerable to ischemia. Perls' reaction with 3,3′-diaminobenzidine intensification revealed iron deposits in the CA, region after week 4, which gradually increased and formed clusters by week 24. Iron also deposited in layers III-V of the parietal cortex after week 8 and gradually built up as granular deposits in the cytoplasm of pyramidal cells in frontocortical layer V. An increasing astroglial reaction and the appearance of ferritin-immunopositive microglia paralleled the iron accumulation in the hippocampal CA, region, indicating that iron deposition was probably produced in the process of gliosis. Neither neuronal death nor atrophy was found in the cerebral cortex. Nevertheless, an astroglial and ferritin-immunopositive microglial reaction became evident at week 8 in the parietal cortex. On the other hand, the granular iron deposition in the pyramidal neurons of frontocortical layer V was not accompanied by any glial reaction in the chronic stage of ischemia. Three different types of iron deposition in the chronic phase after transient forebrain ischemia were shown in this study. In view of the neuronal damage caused by iron-catalyzed free radical formation, the late-onset iron deposition may be relevant to the pathogenesis of the chronic brain dysfunction seen at a late stage after cerebral ischemia.
Regional Cerebral Blood Flow and CO2 Reactivity in Fulminant Hepatic Failure
Authors: Durham Susan , Yonas Howard , Aggarwal Shushma , Darby Joseph , Kramer David
Published: April 2011

Alterations in cerebral hemodynamics are postulated to contribute to brain herniation, a major cause of death in patients with severe hepatic encephalopathy due to fulminant hepatic failure (FHF). In an effort to identify these changes in cerebral hemodynamics, regional and global cerebral blood flow (CBF) and CO2 reactivity were measured using stable xenon-enhanced computed tomography (Xe/CT) in 24 patients within 72 h of onset of severe hepatic encephalopathy. Regional variations in CBF, most notably, a relative decrease in CBF in the anterior circulation and an increase in CBF in the posterior circulation were found. CBF was significantly lower in FHF patients compared with controls, however, these values are well out of the established ischemic range. FHF patients also showed significant impairment in CBF response to hypoventilation, while the CBF response to hyperventilation remained intact. This study suggests that FHF patients demonstrate early changes in both CBF patterns and CO2 reactivity. The relatively “normal” CBF values obtained in FHF patients in severe hepatic encephalopathy coupled with the lack of vasodilatation to hypoventilation suggest a state of uncoupled CBF and metabolism or “luxury perfusion” that could theoretically contribute to vasogenic edema, brain swelling, and cerebral herniation.
Commentary and Opinion: III. Some Nonontological and Functionally Unconnected Views on Current Issues in the Analysis of PET Datasets
Authors: Ford Ian
Published: April 2011

Strother et al. (1995) and Friston (1995) both raise important issues and provide useful reviews of various aspects of PET data analysis. Statisticians would not assume that any single piece of methodology would answer all questions about a type of data in a variety of experimental and observational contexts. The fundamental importance of hypothesis-driven inference, based on well designed experiments, cannot be overestimated for its ability to progress scientific understanding in an orderly manner. However, hypothesis-generating experiments are also vital in their own right. In practice, we generally do not have the luxury of both types of experiment, and we should note Strother et al.'s comment on the importance of extracting as much information as possible from each dataset. Friston (1995) also sees formal testing methods and exploratory methods such as principal components analysis as complementary. The correct approach would therefore seem to be (a) to select methods for formal and exploratory data analysis from the rich existing tool kit of statistical procedures, (b) to modify these as necessary to deal with special PET problems such as multiplicity, (c) to be aware of the assumptions underlying the methods being used and to investigate the problems that can arise if these assumptions fail to hold, (d) to appreciate the complexity of both PET data and of the potential questions that can be asked of it, and (e) to be aware of the limitations of any statistical analysis and the need for caution in interpreting conclusions not based on any predefined hypothesis.
Local Cerebral Glucose Utilization and Cytoskeletal Proteolysis as Indices of Evolving Focal Ischemic Injury in Core and Penumbra
Authors: Yao Hiroshi , Ginsberg Myron D. , Eveleth David D. , LaManna Joseph C. , Watson Brant D. , Alonso Ofelia F. , Loor Judith Y. , Foreman Jill H. , Busto Raul
Published: April 2011

To ascertain the tempo of progression to irreversible injury in focal ischemia, we subjected halothaneanesthetized Sprague–Dawley rats to photochemically induced distal middle cerebral artery occlusion (dMCAO) combined with permanent ipsilateral and 1 h contralateral common carotid artery occlusions. Head temperature was maintained at 36°C. At times centered at either 1.5 or 3 h post-dMCAO, the rate of local glucose metabolism (lCMRgl) was measured by 2-deoxyglucose autoradiography, and cytoskeletal proteolysis was assessed regionally by an immunoblotting procedure to detect spectrin breakdown products. At 1.5 h (n = 5), the cortical ischemic core was already severely hypometabolic (lCMRgl 15.5 ± 10.8 μmol 100 g−1 min−1, mean ± SD), whereas the cortical penumbral zone was hypermetabolic (69.0 ± 9.7). (The lumped constant was verified to be unchanged by methylglucose studies.) Neutral red pH studies at this time point showed that both the core and penumbral zones were equally acidotic. By 3 h post-dMCAO (n = 6), lCMRgl in the penumbral zone had fallen to low levels (15.4 ± 2.2 μmol 100 g−1 min−1) equal to those of the ischemic core (16.7 ± 4.5). Correspondingly, spectrin breakdown in the ischemic core was advanced at both 2 and 3.5 h post-dMCAO (36 ± 18% and 33 ± 18% of total spectrin, respectively), whereas in the penumbral zone spectrin breakdown was less extensive and more highly variable at both times (22 ± 23% and 29 ± 16%). We conclude that irreversible deterioration of the ischemic core, as evidenced by the onset of local cytoskeletal proteolysis, begins within 2 h of middle cerebral artery occlusion. In the ischemic penumbra, the transition from glucose hyper- to hypometabolism occurs by 3.5 h and is associated with a milder and more variable degree of spectrin breakdown.
Astrocytic Swelling Due to Hypotonic or High K+ Medium Causes Inhibition of Glutamate and Aspartate Uptake and Increases Their Release
Authors: Kimelberg Harold K. , Rutledge Eric , Goderie Susan , Charniga Carol
Published: April 2011

Astrocytic swelling occurs readily in ischemia and traumatic brain injury (TBI) as part of the cytotoxic or cellular edema response. Ischemia is known to produce large extracellular increases in both [K+] and excitatory amino acids (EAA) in vivo, and astrocytic swelling in vitro leads to marked release of EAA. In this study we compared the effect of swelling due to hypotonic media and high K+ medium on the uptake and release of EAA by rat primary astrocyte cultures in vitro. In both cases, there was a significant inhibition of uptake of [3H]l-glutamate and [3H]d-aspartate, and increased release of preloaded [3H]d-aspartate. The kinetics of the increased efflux was very different in response to hypotonic or high K+ media. In hypotonic medium there was a rapid initial release followed by a decline in the rate of release over time. This release was independent of whether Na+ was present. Upon exposure to high K+ medium there was a slow progressive increase in release of [3H]d-aspartate, which never showed any subsequent decline until the media was returned to normal [K+]. In high K+ media there was also an initial transient increase in [3H]d-aspartate release, which we attribute to reversal of the amino acid uptake system. The increased release due to hypotonic medium was not affected by a drop in temperature from 37 to 26°C, while the increased release due to high K+ medium was completely inhibited. The decreased uptake and increased release of EAA when astrocytes swell will short-circuit a presumed important, protective uptake system for EAA and may contribute to the increased levels of extracellular EAA seen during ischemia, TBI, and other pathologic states.
Acidosis Causes Failure of Astrocyte Glutamate Uptake during Hypoxia
Authors: Swanson Raymond A. , Farrell Kevin , Simon Roger P.
Published: April 2011

Failure of glutamate uptake during ischemia can lead to neurotoxic accumulations of glutamate in brain extracellular space. Hypoxia and acidosis are metabolic consequences of ischemia that may individually or in combination impair glutamate uptake. We used primary rat astrocyte cultures to study the effects of acidosis, chemical hypoxia, and the combination of acidosis plus chemical hypoxia on glutamate uptake. Chemical hypoxia alone reduced uptake by 35–45%. Reduction in pH from 7.4 to 5.8 also caused a significant but incomplete inhibition of glutamate uptake, and this effect was more pronounced in medium buffered with CO2/ bicarbonate. However, the combination of chemical hypoxia plus acidosis reduced glutamate uptake to below 10% of controls. Astrocyte ATP levels, like glutamate uptake, were significantly reduced by chemical hypoxia and further reduced by the combination of hypoxia plus acidosis. Acidosis under normoxic conditions had no significant effect on astrocyte ATP levels. These results suggest two mechanisms by which acidosis may contribute to failure of astrocyte glutamate uptake during ischemia: Acidosis may act in concert with hypoxia to cause ATP depletion, and acidosis may also have direct effects on glutamate transporters unrelated to effects on cellular ATP levels. pH effects on glutamate uptake may be an important factor affecting neuronal survival during incomplete ischemia.
Protective Effects of Antiarrhythmic Agents against Anoxic Injury in CNS White Matter
Authors: Stys Peter K.
Published: April 2011

Irreversible anoxic injury is dependent on extracellular Ca2+ in mammalian CNS white matter, with a large portion of the pathologic Ca2+ influx occurring through reverse Na+ –Ca2+ exchange, stimulated by increased intracellular [Na+]. This Na+ leak likely occurs via incompletely inactivated voltage-gated Na+ channels. This study reports that clinically used antiarrhythmic compounds, likely by virtue of their Na+ channel– blocking properties, significantly protect CNS white matter from anoxia at concentrations that cause little suppression of the preanoxic response. Rat optic nerves were pretreated with various agents for 60 min, then subjected to 60 min of anoxia in vitro. Functional recovery was measured electrophysiologically as the area under the compound action potential (CAP). Without drug, the CAP areas recovered to a mean of 32 ± 12% of control after 1 h of reoxygenation. Recoveries using prajmaline 10 μ M were 82 ± 15% ( p < 0.0001), and using tocainide 1 m M, 78 ± 8% (p < 0.0001), with little suppression (≤10%) of the preanoxic response. Ajmaline (10–100 μ M), disopyramide (10–300 μ M) and bupivacaine (10–100 μ M) were somewhat less effective, whereas verapamil produced 52 ± 11% recovery before reduction of the preanoxic CAP was observed at 30 μ M. Procainamide (100– 300 μ M) was ineffective. These results suggest that Na+ channel blockers, including commonly used antiarrhythmic agents, may be effective in protecting central white matter, which is a target for anoxic/ischemic injury in diseases such as stroke and spinal cord injury.
Effect of Cerebral Ischemia on Calcium/Calmodulin-Dependent Protein Kinase II Activity and Phosphorylation
Authors: Shackelford D. A. , Yeh R. Y. , Hsu M. , Buzsáki G. , Zivin J. A.
Published: April 2011

The effects of cerebral ischemia on calcium/calmodulin-dependent kinase II (CaM kinase II) were investigated using the rat four-vessel occlusion model. In agreement with previous results using rat or gerbil models of cerebral ischemia or a rabbit model of spinal cord ischemia, this report demonstrates that transient forebrain ischemia leads to a reduction in CaM kinase II activity within 5 min of occlusion onset. Loss of activity from the cytosol fractions of homogenates from the neocortex, striatum, and hippocampus correlated with a decrease in the amount of CaM kinase α and β isoforms detected by immunoblotting. In contrast, there was an apparent increase in the amount of CaM kinase α and β in the particulate fractions. The decrease in the amount of CaM kinase isoforms from the cytosol but not the particulate fractions was confirmed by autophosphorylation of CaM kinase II after denaturation and renaturation in situ of the blotted proteins. These results indicate that ischemia causes a rapid inhibition of CaM kinase II activity and a change in the partitioning of the enzyme between the cytosol and particulate fractions. CaM kinase II is a multifunctional protein kinase, and the loss of activity may play a critical role in initiating the changes leading to ischemia-induced cell death.

To identify a structural basis for the decrease in enzyme activity, tryptic peptide maps of CaM kinase II phosphorylated in vitro were compared. Phosphopeptide maps of CaM kinase α from particulate fractions of control and ischemic samples revealed not only reduced incorporation of phosphate into the protein but also the absence of a limited number of peptides in the ischemic samples. This suggested that certain sites are inaccessible, possibly due to a conformational change, a covalent modification of CaM kinase II, or steric hindrance by an associated molecule. Verifying one of these possibilities should help to elucidate the mechanism of ischemia-induced modulation of CaM kinase II.
Long-Term Spatial Cognitive Impairment following Middle Cerebral Artery Occlusion in Rats. A Behavioral Study
Authors: Okada Mitsuko , Tamura Akira , Urae Akinori , Nakagomi Tadayoshi , Kirino Takaaki , Mine Kazunori , Fujiwara Michihiro
Published: April 2011

Behavioral changes in the chronic phase of permanent occlusion of the right middle cerebral artery (MCA) in rats were investigated. One month after MCA occlusion, 23 rats were unable and 7 rats were able to solve a radial 8-arm maze task during a 1-month period. Three months after occlusion, 19 MCA-occluded rats failed to solve the task successfully again during at least a 1-month period (the cognitively impaired rats), and 11 MCA-occluded rats were able to solve it (the cognitively unimpaired rats). When a delay of 60 min was imposed for this task, five cognitively unimpaired rats failed to solve it. The locomotor activity of the cognitively impaired rats increased significantly 2 months after occlusion, and this increase showed good correlation with spatial cognitive deficit. However, the mean time a rat spent at each arm remained unchanged among the cognitively impaired, unimpaired, and sham-operated rats. There was no significant difference in the ratio between the cognitively impaired and unimpaired rats for disturbed motor coordination. These results suggest that MCA occlusion is capable of producing long-term spatial cognitive disturbance in rats. In addition, this spatial cognitive deficit does not seem to be primarily due to hypermotility or a disturbance in motor coordination.
Contribution of Cerebrovascular Parasympathetic and Sensory Innervation to the Short-Term Control of Blood Flow in Rat Cerebral Cortex
Authors: Branston Neil M. , Umemura Atsushi , Koshy Achamma
Published: April 2011

In two groups of normotensive rats anaesthetised with halothane, either the nasociliary nerve (NCN) or the NCN and parasympathetic (PS) fibres together (NCN-PS) were functionally blocked at the right ethmoidal foramen. Blocking was achieved reversibly and repeatedly using a cooling probe. Cortical regional CBF (rCBF) was measured bilaterally using laser–Doppler probes. In Group 1, bilateral common carotid occlusion (CCO) was applied for 1 min both with and without block. In Group 2, CCO was applied permanently followed by stages of controlled haemorrhagic hypotension to deepen the ischaemia and the block applied at each stage. In Group 1, during CCO, rCBF was unaffected by blocking NCN-PS. However, during the transient postocclusive hyperaemia, blocking NCN-PS, but not NCN alone, significantly increased right side rCBF. In Group 2 and in Group 1 in the absence of CCO (normotension), rCBF was unaffected by blocking either set of fibres. We conclude that neither NCN nor PS fibres contribute to the tonic level of rCBF or to its autoregulatory control, but PS fibres conduct impulses tending to resolve postischaemic hyperaemia. We suggest that a subpopulation of PS fibres containing neuropeptide Y is activated under conditions of supernormal rCBF.
Attenuation of Stroke Size in Rats Using an Adenoviral Vector to Induce Overexpression of Interleukin-1 Receptor Antagonist in Brain
Authors: Betz A. Lorris , Yang Guo-Yuan , Davidson Beverly L.
Published: April 2011

Adenoviruses have been proposed as potential vectors for gene therapy in the central nervous system, but there are no reports of their use in the treatment of a brain disease. Because central administration of interleukin-1 receptor antagonist protein (IL-1ra) reduces ischemic brain damage, we determined whether a recombinant adenovirus vector carrying the human IL-1ra cDNA (Ad.RSV IL-1ra) could be used to ameliorate brain injury in permanent focal ischemia. Groups of six rats received intraventricular injections of Ad.RSV IL-1ra or a control adenovirus containing the Escherichia coli β-galactosidase gene (Ad.RSV lacZ). Histochemical staining for β-galactosidase 5 days after virus injection indicated that transgene expression was confined primarily to the cells lining the ventricle. The concentrations of IL-1ra were fivefold to 50-fold higher in the Ad.RSV IL-1ra-injected animals, achieving levels of 9.1 ± 3.3 ng/g in brain and 23.7 ± 22.5 ng/ml in CSF. In these animals, cerebral infarct volume resulting from 24 h of permanent middle cerebral artery occlusion was reduced 64%. These studies demonstrate that adenoviral vectors can be used to deliver genes that attenuate brain injury.
Three-Dimensional Image Analysis of Brain Glucose Metabolism-Blood Flow Uncoupling and its Electrophysiological Correlates in the Acute Ischemic Penumbra following Middle Cerebral Artery Occlusion
Authors: Back Tobias , Zhao Weizhao , Ginsberg Myron D.
Published: April 2011

The relationship between local cerebral glucose utilization (LCMRglc) and local CBF (LCBF) is known to be disturbed in regions surrounding an acute focal ischemic lesion—areas that undergo repeated transient depolarizations. In this study, we evaluated the relationship between LCMRglc and LCBF in the acute focal ischemic penumbra to quantify metabolism–flow uncoupling, and we related these findings to local electrophysiological measurements. A novel strategy utilizing three-dimensional (3D) autoradiographic image averaging yielded group 3D reconstructions of LCBF, LCMRglc, and the CMR/CBF ratio. The distal right middle cerebral artery of Sprague-Dawley rats was occluded by laser-driven photothrombosis following administration of the photosensitizing dye rose bengal; this was coupled with permanent ipsilateral and 1-h contralateral common carotid artery occlusions. LCBF (n = 7) and LCMRglc (n = 7) were measured autoradiographically at 1.25 and 1.5–2 h postocclusion, respectively, in matched animal groups. Within the ischemic penumbra (defined as having LCBF of 20–40% of control or 0.23–0.47 ml g−1 min−1), LCMRglc showed a heterogeneous pattern with values ranging from near normal to markedly increased. The resulting CMRglc/CBF ratio in this zone was 234 ± 100 μmol/100 ml (mean ± SD), representing a severe degree of metabolism-flow dissociation when compared with the CMRglc/CBF ratio of 51.0 ± 28.7 μmol/100 ml of the contralateral (normal) hemisphere. Metabolism–flow uncoupling was confined to the ipsilateral cortex and was most prominent at the anterior and posterior coronal poles of the ischemic lesion. In the frontoparietal penumbra, where marked uncoupling was observed, sustained deflections of the DC potential were recorded, which increased significantly in duration over the initial 65 min postocclusion. Both the heterogeneous pattern of LCMRglc and the widespread distribution of increased CMRglc/CBF ratio in the ischemic penumbra are thought to reflect the metabolic consequences of periinfarct depolarizations. Analysis of averaged 3D autoradiographic data sets provides a powerful means for assessing metabolism-flow uncoupling surrounding an ischemic focus.