bluuebunny/crossref_metadata_2025 huggingface dataset:
Altered Cerebral Blood Flow and Glucose Metabolism in Patients with Liver Disease and Minimal Encephalopathy
Authors: Lockwood Alan H. , Yap Eddy W. H. , Rhoades Howard M. , Wong Wai-Hoi
Published: April 2011

We measured CBF and the CMRglc in normal controls and in patients with severe liver disease and evidence for minimal hepatic encephalopathy using positron emission tomography. Regions were defined in frontal, temporal, parietal, and visual cortex; the thalamus; the caudate; the cerebellum; and the white matter along with a whole-slice value obtained at the level of the thalamus. There was no difference in whole-slice CBF and CMRglc values. Individual regional values were normalized to the whole-slice value and subjected to a two-way repeated measures analysis of variance. When normalized CBF and CMRglc values for regions were compared between groups, significant differences were demonstrated ( F = 5.650, p = 0.00014 and F = 4.58, p = 0.0073, respectively). These pattern differences were due to higher CBF and CMRglc in the cerebellum, thalamus, and caudate in patients and lower values in the cortex. Standardized coefficients extracted from a discriminant function analysis permitted correct group assignment for 95.5% of the CBF studies and for 92.9% of the CMRglc studies. The similarity of the altered pattern of cerebral metabolism and flow in our patients to that seen in rats subjected to portacaval shunts or ammonia infusions suggests that this toxin may alter flow and metabolism and that this, in turn, causes the clinical expression of encephalopathy.
Effect of Subarachnoid Hemorrhage on Serotonin Uptake and Metabolism in Rabbit Basilar Artery
Authors: Tanaka Yuichiro , Kassell Neal F. , Machi Takao , Dougherty Douglas A.
Published: April 2011

The effects of subarachnoid hemorrhage (SAH) on neuronal uptake and metabolism of serotonin (5-HT) in the rabbit basilar artery were examined. Extracted 3H-amines from the isolated arteries after incubation with [3H]5-HT were separated by column chromatography. Radioactivity of 5-HT and 5-hydroxyindoleacetic acid was, respectively, 52.7 ± 13.9 and 22.9 ± 5.4 × 102 dpm/mg tissue in the control group (n = 8); 32 and 18% of control after denervation (n = 6); 99 and 12% of control after treatment with pargyline (n = 7); and 65 and 76% of control after SAH (n = 7). These results suggest that the neuronal uptake of 5-HT is impaired by SAH, although monoamine oxidase activity is relatively preserved.
Three-Dimensional Reconstruction of the Rat Brain Cortical Microcirculation in vivo
Authors: Dirnagl Ulrich , Villringer Arno , Gebhardt Roland , Haberl Roman L. , Schmiedek Peter , Einhäupl Karl M.
Published: April 2011

We used confocal laser scanning microscopy (CLSM) to investigate the morphology and three-dimensional relationships of the microcirculation of the superficial layers of the rat brain cortex in vivo. In anesthetized rats equipped with a closed cranial window (dura mater removed), after i.v. injection of 3 mg/100 g of body weight of fluorescein in 0.5 ml of saline, serial optical sections of the brain cortex intraparenchymal microcirculation were taken. Excitation was at a wavelength of 488 nm (argon laser), and emission was collected above 515 nm. CLSM provided images of brain vessels with sufficient signal-to-noise ratio for three-dimensional reconstructions down to a depth of 250 μm beneath the surface of the brain. Compared to conventional fluorescence microscopy, CLSM has a much higher axial resolution and higher depth of penetration. Laser light-induced intravascular aggregates, irregularities of erythrocyte flow, or microvascular occlusions (“light and dye injury”) were not apparent in the current experimental paradigm. CLSM is a promising new tool for in vivo visualization of the cerebral microcirculation. Future studies have to characterize the potential damage to the tissue caused by the cranial window preparation and light and dye mechanisms.
Nitric Oxide Mediates the Neurogenic Vasodilation of Bovine Cerebral Arteries
Authors: Gonzalez Carmen , Estrada Carmen
Published: April 2011

Nitric oxide (NO) is a mediator of the vasodilation induced by a variety of physiological and pharmacological stimuli. The possible role of NO in the relaxation elicited in cerebral arteries by perivascular nerve stimulation has been investigated. Electrical field stimulation of precontracted bovine cerebral arteries induced a relaxation that was blocked by tetrodotoxin, but not by adrenergic or muscarinic receptor antagonists, suggesting the existence of nonadrenergic, noncholinergic dilator nerves, as has been shown in other species. The relaxation was significantly reduced by the inhibitors of NO synthesis, NG-monomethyl-L-arginine and nitro-L-arginine methyl ester, but not by the enantiomer, NG-monomethyl-D-arginine. Such a reduction was reversed by L-arginine. In addition, transmural nerve stimulation (TNS)-induced relaxation was potentiated by superoxide dismutase. No response to TNS was observed in arteries without endothelium. These results suggested that neurogenic relaxation of bovine cerebral arteries is mediated by endothelium-derived NO.
Ischemic Brain Slice Glucose Utilization: Effects of Slice Thickness, Acidosis, and K+
Authors: Newman George C. , Hospod Frank E. , Schissel Scott L.
Published: April 2011

Brain slices of varying thickness were used to modify retention of metabolic products in an in vitro model of ischemia. Past and present results reveal increased anaerobic glycolysis in 660-μm slices with accumulation of lactate as slice thickness reaches 1,000 μm. Brain slice glucose utilization and lactate content were measured in buffers of various extracellular K+ levels and pH in 540-, 660-, and 1,000-μm slices. Acidosis suppresses glucose utilization at all slice thicknesses without affecting tissue lactate. Studies of 2-deoxyglucose metabolites establish that the suppression of glucose utilization by acidosis is due entirely to inhibition of glucose phosphorylation without any effect on glucose uptake into tissue. The inhibition is reversible after 45 min at pH 6.1. The experiments with acidosis also suggest that persistent energy demands continue to stimulate phosphofructokinase despite the low pH so that glycolysis continues, with potential for injury. Increasing K+ increases glucose utilization and tissue lactate at all three thicknesses. Correlations of glucose utilization with lactate accumulation support the possibility that high K+ may exert a dual influence on the tissue metabolism, not only stimulating glucose utilization by inducing depolarization but also by influencing the removal of metabolic products.
EEG Suppression and Anoxic Depolarization: Influences on Cerebral Oxygenation during Ischemia
Authors: Raffin Cesar N. , Harrison Madaline , Sick Thomas J. , Rosenthal Myron
Published: April 2011

Cerebral ischemia provokes sequential changes that include EEG suppression, anoxic depolarization (AD) with maximal increases in extracellular potassium ion activity (K+o), and anoxia with maximal decreases in tissue oxygen tension (tPO2) and increases in the reduction/oxidation (redox) ratios of the mitochondrial electron transport carriers. Studies were directed toward relationships among these events during cerebral ischemia (“four-vessel occlusion model”) in pentobarbital anesthetized rats. Results demonstrate that EEG suppression and anoxic depolarization do not occur as a simple function of progressive oxygen decline during cerebral ischemia. Rates of K+ elevation, tPO2 decline, and cytochrome a,a3 reduction were decreased in the immediate period following EEG suppression. Latency to EEG suppression was inversely correlated with latency to maximal cytochrome reduction. In contrast, AD was associated with increased rates of tPO2 decline and cytochrome a,a3 reduction. Latency to AD was related to latency of subsequent maximal cytochrome a,a3 reduction. These data suggest that EEG suppression spares oxygen while AD accelerates the progression to energy failure by accelerating the decline in oxygen stores in brain following global ischemia.
Localization of 70 kDa Stress Protein mRNA Induction in Gerbil Brain after Ischemia
Authors: Nowak Thaddeus S.
Published: April 2011

Induction of mRNA encoding the 70 kDa stress/heat shock protein, hsp70, was evaluated in postischemic gerbil brain by in situ hybridization using an oligonucleotide probe selective for stress-inducible members of this gene family. Expression of hsp70 sequences was most pronounced in hippocampal CA1 neurons that fail to accumulate immunoreactive hsp70 protein, and that are selectively lost following ischemia. Hybridizable RNA continued to be expressed in CA1 through at least 48 h, essentially until the onset of cell death in this model. In contrast, dentate granule cells and CA3 neurons destined to survive the insult showed transient induction of hsp70 mRNA during the first 24 h of recirculation that disappeared prior to the detection of maximal hsp70 immunoreactivity in these cell populations. Pre treatment with a single injection of MK-801 (10 mg/kg) considerably attenuated the induction of hsp70 mRNA in hippocampus at 6 h of recirculation, an effect apparently mediated by persistent drug-induced hypothermia. The drug did not prevent the later, selective appearance of hsp70 hybridization in CA1 neurons at 24 h, nor did it protect against the subsequent loss of these cells. These results demonstrate a prolonged postischemic stress response at the transcriptional level in vulnerable hippocampal neurons, and suggest its utility as a marker for neuronal pathophysiology associated with mechanisms mediating delayed neuronal death.
Basic Fibroblast Growth Factor Prevents Thalamic Degeneration after Cortical Infarction
Authors: Yamada Kazuo , Kinoshita Akira , Kohmura Eiji , Sakaguchi Tateo , Taguchi Junji , Kataoka Kazuo , Hayakawa Toru
Published: April 2011

In the focal infarction model of the rat middle cerebral artery (MCA), the thalamus of the occluded side becomes gradually atrophic, mainly because of retrograde degeneration. We determined whether basic fibroblast growth factor (bFGF) administered intracisternally could prevent this thalamic atrophy. We occluded the left MCA through a small cranial opening, and animals were then divided into two groups. One group received intra-cisternal injections of recombinant bFGF (1 μg dissolved in 0.1 ml of saline with 2% rat serum) starting 1 day after occlusion and repeated once a week to a total dose of 4 μg by four injections. The other group received vehicle solution by the same schedule. The animals were perfused and fixed at 28 days after occlusion, and histological examination was made at the level of the caudoputamen and thalamus. In the bFGF-treated rats, the area of the posterior ventral thalamus of the occluded side was 93% of that of the contralateral side, i.e., significantly larger than in the normal saline-treated rats (75%, p < 0.01). The infarction size was not statistically different in the two groups. Microscopic observation indicated that normal-saline-treated animals showed shrinkage and disappearance of thalamic neurons, whereas bFGF-treated groups showed preservation of thalamic neurons. Computerized analysis of the cell size substantiated this observation. To assess the effect of bFGF on astrocytes, bFGF or vehicle solution was injected into normal rats, and their histology was evaluated at 1, 2, and 4 weeks after injection. The bFGF-injected group showed a significant increase in glial fibrillary acidic protein-positive astrocytes in the brain tissue facing the ventriculocisternal system. The results suggest that bFGF prevents retrograde degeneration of thalamic neurons by working directly as a neurotrophic factor of these neurons or by activating astrocytes located in the thalamocortical pathway.
A New Approach of Weighted Integration Technique Based on Accumulated Images Using Dynamic PET and H152O
Authors: Yokoi Takashi , Kanno Iwao , Iida Hidehiro , Miura Shuichi , Uemura Kazuo
Published: April 2011

We developed a new technique of weighted integration for the measurement of local cerebral blood flow (LCBF) and the blood-tissue partition coefficient ip) using dynamic positron emission tomography (PET) and H152O. The weighted integration in the new technique is carried out on the equation of the first time integration of the Kety–Schmidt differential equation. Practically, serially accumulated images with sequentially prolonged accumulation times are weighted by two arbitrary functions. The weighting functions do not have to be differentiated because of the exclusion of the differential term in the starting equation. Consequently, the method does not require data at the end of the scan. The technique was applied to H152O dynamic PET performed on four normal subjects, and was verified to provide a better signal-to-noise ratio than the previously developed integrated projection (IP) technique. Computer simulations were carried out to investigate the effects of statistical noise, tissue heterogeneity, and time delay and dispersion in arterial input function. The simulation showed that the new technique provided about a 1.4 times lower statistical error in both LCBF and p at 50 ml 100 g−1 min−1 compared to the IP technique, and it should be noted that the new technique was less sensitive to the shape of the weighting functions. The new technique provides a new strategy with respect to the statistical error for estimation of LCBF and p.
Human Regional Cerebral Blood Flow during Rapid-Eye-Movement Sleep
Authors: Madsen Peter Lund , Holm Søren , Vorstrup Sissel , Friberg Lars , Lassen Niels A. , Wildschiødtz Gordon
Published: April 2011

Owing to the coupling between CBF and neuronal activity, regional CBF is a reflection of neural activity in different brain regions. In this study we measured regional CBF during polysomnographically well-defined rapid-eye-movement (REM) sleep by the use of single photon emission computerized tomography and the new tracer 99mTc- dl-hexamethylpropyleneamine. Eleven healthy volunteers aged between 22 and 27 years were studied. CBF was measured on separate nights during REM sleep and during EEG-verified wakefulness. On awakening from REM sleep, all subjects reported visual dreams. During REM sleep CBF increased by 4% (p < 0.01) in the associative visual area, while it decreased by 9% (p < 0.01) in the inferior frontal cortex. The CBF increase in the associative visual area suggests that activation of cerebral structures processing complex visual material is correlated to visual dream experiences. On the other hand, the reduced involvement of the inferior frontal cortex observed during REM sleep might explain the poor temporal organization and bizarreness often experienced in dreams.
99mTc-d,l-HMPAO and SPECT of the Brain in Normal Aging
Authors: Waldemar Gunhild , Hasselbalch Steen G. , Andersen Allan R. , Delecluse Florence , Petersen Palle , Johnsen Anni , Paulson Olaf B.
Published: April 2011

Single photon emission computed tomography (SPECT) with 99mTc- d,l-hexamethylpropyleneamine oxime (99mTc- d,l-HMPAO) was used to determine global and regional CBF in 53 healthy subjects aged 21–83 years. For the whole group, global CBF normalized to the cerebellum was 86.4% ± 8.4 (SD). The contribution of age, sex, and atrophy to variations in global CBF was studied using stepwise multiple regression analysis. There was a significant negative correlation of global CBF with subjective ratings of cortical atrophy, but not with ratings of ventricular size, Evans ratio, sex, or age. In a subgroup of 33 subjects, in whom volumetric measurements of atrophy were performed, cortical atrophy was the only significant determinant for global CBF, accounting for 27% of its variance. Mean global CBF as measured with the 133Xe inhalation technique and SPECT was 54 ± 9 ml/100 g/min and did not correlate significantly with age. There was a preferential decline of CBF in the frontal cortex with advancing age. The side-to-side asymmetry of several regions of interest increased with age. A method was described for estimation of subcortical CBF, which decreased with advancing cortical atrophy. The relative area of the subcortical low-flow region increased with age. These results are useful in distinguishing the effects of age and simple atrophy from disease effects, when the 99mTc- d,l-HMPAO method is used.
Stable Xenon Does Not Increase Intracranial Pressure in Primates with Freeze-Injury-Induced Intracranial Hypertension
Authors: Darby Joseph M. , Nemoto Edwin M. , Yonas Howard , Melick John
Published: April 2011

Stable xenon (Xe)-enhanced computed tomography is a potentially valuable tool for high resolution, three-dimensional measurement of CBF in patients. However, reports that Xe causes cerebrovascular dilation and increases intracranial pressure (ICP) have tempered enthusiasm for its use. The effects of 5 min of 33% Xe inhalation on ICP (right and left hemispheres) were studied in eight fentanyl-anesthetized Rhesus monkeys after right-sided cortical freeze injury. ICP, CBF, and physiological variables were monitored for up to 6 h postinsult. The preinjury (control) right hemispheric ICP was 8 ± 5 mm Hg (mean ± SD) and left hemispheric ICP was 5 ± 2 mm Hg. Postinjury observations were classified into low (<15 mm Hg) and high ICP (≤ 15 mm Hg) groups. Both right and left ICP values averaged 9 ± 3 mm Hg in the low ICP group. In the high ICP group, the right ICP was 20 ± 4 mm Hg and left ICP was 21 ± 6 mm Hg. ICP was unchanged by Xe inhalation under control conditions as well as in both low and high ICP groups postinjury. Postinjury, the MABP decreased 10–15 mm Hg in the low ICP group and 10–17 mm Hg in the high ICP group 2–3 min after the start of Xe inhalation (p < 0.05). These results show that 33% Xe inhalation does not increase ICP in fentanyl-anesthetized monkeys but could decrease MABP in stressed states, presumably because of the anesthetic effects of Xe.
Dihydrolipoate Reduces Neuronal Injury after Cerebral Ischemia
Authors: Prehn Jochen H. M. , Karkoutly Chourouk , Nuglisch Jörg , Peruche Barbara , Krieglstein Josef
Published: April 2011

It has been shown in vitro that dihydrolipoate (dl-6,8-dithioloctanoic acid) has antioxidant activity against microsomal lipid peroxidation. We tested dihydrolipoate for its neuroprotective activity using models of hypoxic and excitotoxic neuronal damage in vitro and rodent models of cerebral ischemia in vivo. In vitro, neuronal damage was induced in primary neuronal cultures derived form 7-day-old chick embryo telencephalon by adding either 1 m M cyanide or 1 m M glutamate to the cultures. Cyanide-exposed and dihydrolipoate-treated (10−9–10−7 M) cultures showed an increased protein and ATP content compared with controls. The glutamate-exposed cultures treated with dihydrolipoate (10−7–10−5 M) showed a decreased number of damaged neurons. In vivo, dihydrolipoate treatment (50 and 100 mg/kg) reduced brain infarction after permanent middle cerebral artery occlusion in mice and rats. Dihydrolipoate treatment (50 and 100 mg/kg) could not ameliorate neuronal damage in the rat hippocampus or cortex caused by 10 min of forebrain ischemia. A comparable neuroprotection was obtained by using dimethylthiourea, both in vitro (10−7 and 10−6 M) and at a dose of 750 mg/kg in the focal ischemia models. Lipoate, the oxidized form of dihydrolipoate, failed to reduce neuronal injury in any model tested. We conclude that dihydrolipoate, similarly to dimethylthiourea, is able to protect neurons against ischemic damage by diminishing the accumulation of reactive oxygen species within the cerebral tissue.
Extracellular Antioxidants and Amino Acids in the Cortex of the Rat: Monitoring by Microdialysis of Early Ischemic Changes
Authors: Landolt H. , Lutz T. W. , Langemann H. , Stäuble D. , Mendelowitsch A. , Gratzl O. , Honegger C. G.
Published: April 2011

Extracellular concentrations of ascorbic acid, glutathione, cysteine, uric acid, tyrosine, and tryptophan were monitored using intracerebral microdialysis in the left frontoparietal cortex of spontaneous hypertensive rats before, and for 3 h after, either focal ischemia [left middle cerebral artery occlusion (MCAO)] or sham operation. The size of the ischemic area and the position of the microdialysis probe were checked using the enzyme histotopochemical acid phosphatase reaction. The probe was always located in the cortex inside the stained area. Ascorbic acid levels rose immediately after MCAO and remained at about 12-fold for 3 h. There was a transient release of glutathione during 1–1.5 h. Uric acid concentrations were also increased but the differences did not reach significance. The levels of the amino acids tyrosine and tryptophan increased steadily after MCAO. The increases in cysteine were variable but significant. In some experiments, the pH of the dialysate was measured online. The parameters ascorbic acid, glutathione, cysteine, and pH are suitable for the early detection of cortical ischemic events by microdialysis.
Regional Expression of c-Fos and Heat Shock Protein-70 mRNA following Hypoxia-Ischemia in Immature Rat Brain
Authors: Blumenfeld Ken S. , Welsh Frank A. , Harris Valerie A. , Pesenson Michael A.
Published: April 2011

Cerebral ischemia induces the expression of a number of proteins that may have an important influence on cellular injury. The purpose of this study was to compare the regional effects of hypoxia–ischemia on the expression of the proto-oncogene, c-fos, and the heat shock protein-70 (HSP-70) gene in developing brain. Unilateral hypoxia–ischemia was produced in the brain of immature rats (7, 15, and 23 days after birth) using a combination of carotid artery ligation and systemic hypoxia (8% O2). After recovery for 2 and 24 h, the regional expression of c-fos and HSP-70 mRNA was determined using in situ hybridization. Littermates were permitted to recover for 1 week for assessment of histologic injury. Hypoxia–ischemia increased the expression of both c-fos and HSP-70 mRNA, but the topography of expression varied with the age of the animal as well as the mRNA species. In the 7-day-old group, expression of c-fos at 2 h increased in multiple regions of the ipsilateral hemisphere in nearly one-half of the animals, while HSP-70 mRNA was not expressed until 24 h and, then, predominantly in the hippocampus. In 15- and 23-day-old rats, expression of c-fos was increased at 2 h in the entorhinal cortex and in the dendritic field of the upper blade of the hippocampal dentate gyrus, while HSP-70 mRNA was prominently expressed in neocortex and the cell layers of the hippocampus. Interestingly, the strong expression of HSP-70 mRNA in dentate granule cells did not occur in the innermost layer of cells. By 24 h of recovery, expression of c-fos had nearly normalized in all age groups, while HSP-70 mRNA was expressed in 15- and 23-day-old rats in many regions, including those undergoing histologic injury. These results suggest that expression of c-fos and HSP-70 mRNA may be useful regional markers of cell stress following hypoxia–ischemia.
Cerebral Lactate Turnover after Electroshock: In vivo Measurements by 1H/13C Magnetic Resonance Spectroscopy
Authors: Petroff Ognen A. C. , Novotny Edward J. , Avison Malcolm , Rothman Douglas L. , Alger Jeffry R. , Ogino Takashi , Shulman Gerald I. , Prichard James W.
Published: April 2011

We reported earlier that brain activation by 10 s of cortical electroshock caused prolonged elevation of brain lactate without significant change in intracellular pH, brain high-energy phosphorylated metabolites, or blood gases. The metabolic state of the elevated lactate has been investigated in further experiments using combined, in vivo 1H-observed 13C-edited nuclear magnetic resonance spectroscopy (NMRS), homonuclear J-edited 1H-NMRS, and high-resolution 1H-NMRS of perchloric acid extracts to monitor concentrations and 13C-isotopic fractions of brain and blood lactate and glucose. We now report that electroshock-elevated lactate pool in rabbit brain approaches equilibrium with blood glucose within 1 h. There was nearly complete turnover of the raised lactate pool in brain; any pool of metabolically inactive lactate could not have been >5% of the total. In the same experiments, blood lactate underwent <50% turnover in 1 h. The new 1H-spectroscopic methods used for these experiments are readily adaptable for the study of human brain and may be useful in characterizing the metabolic state of elevated lactate pools associated with epilepsy, stroke, trauma, tumors, and other pathological conditions.
Effect of Dichloroacetate on Recovery of Brain Lactate, Phosphorus Energy Metabolites, and Glutamate during Reperfusion after Complete Cerebral Ischemia in Rats
Authors: Chang Lee-Hong , Shimizu Hiroaki , Abiko Hisashi , Swanson Raymond A. , Faden Alan I. , James Thomas L. , Weinstein Philip R.
Published: April 2011

The effects of dichloroacetate (DCA) on brain lactate, intracellular pH (pHi), phosphocreatine (PCr), and ATP during 60 min of complete cerebral ischemia and 2 h of reperfusion were investigated in rats by in vivo 1H and 31P magnetic resonance spectroscopy; brain lactate, water content, cations, and amino acids were measured in vitro after reperfusion. DCA, 100 mg/kg, or saline was infused before or immediately after the ischemic period. Preischemic treatment with DCA did not affect brain lactate or pHi during ischemia, but reduced lactate and increased pHi after 30 min of reperfusion ( p < 0.05 vs. controls) and facilitated the recovery of PCr and ATP during reperfusion. Postischemic DCA treatment also reduced brain lactate and increased pHi during reperfusion compared with controls ( p < 0.05), but had little effect on PCr, ATP, or Pi during reperfusion. After 30 min of reperfusion, serum lactate was 67% lower in the postischemic DCA group than in controls ( p < 0.05). The brain lactate level in vitro was 46% lower in the postischemic DCA group than in controls ( p < 0.05). DCA did not affect water content or cation concentrations in either group, but it increased brain glutamate by 40% in the preischemic treatment group ( p < 0.05). The potential therapeutic effects of DCA on brain injury after complete ischemia may be mediated by reduced excitotoxin release related to decreased lactic acidosis during reperfusion.
A Comparison of Regional Cerebral Blood Flow and Middle Cerebral Artery Blood Flow Velocities: Simultaneous Measurements in Healthy Subjects
Authors: Dahl Arve , Russell David , Nyberg-Hansen Rolf , Rootwelt Kjell
Published: April 2011

Blood flow velocities were measured in both middle cerebral arteries (MCAs) of 36 healthy subjects using transcranial Doppler ultrasound. Measurements were first made using a hand-held probe. Velocities were then studied bilaterally with fixed probes under resting conditions and during simultaneous regional CBF (rCBF) measurements. A significant (p < 0.05) positive correlation was found between MCA flow velocities and rCBF in the estimated perfusion territory of this artery. The correlation coefficient was highest when the measurements were performed simultaneously (p < 0.001) or when velocities recorded with a hand-held probe were adjusted to take into account the significant velocity increase induced by the CBF study situation. The increased velocities during CBF measurements cannot be fully explained by the moderate but significant Pco2 increase. Other possible mechanisms are increased blood flow due to mental activation or MCA vasoconstriction secondary to stimulation of the sympathetic nervous system. The effect of mental activation and Pco2 differences should therefore be considered when comparing the results of repeated velocity and CBF measurements.
Validation of 133Xe Clearance as a Cerebral Blood Flow Measurement Technique during Cardiopulmonary Bypass
Authors: Spahn Donat R. , Quill Timothy J. , Hu Wei-Chih , Lu Joseph , Smith L. Richard , Reves J. G. , McRae Robert L. , Leone Bruce J.
Published: April 2011

133Xe clearance to measure cerebral blood flow (CBF) was examined in 10 dogs during cardiopulmonary bypass. As a reference method, a continuous Kety–Schmidt technique (CBFKS) with 133Xe as indicator was used. Extracranial tissue was removed to directly place the 133Xe detectors on the skull, and the head was covered with a 3 mm lead shield to minimize contamination of the 133Xe clearance curve with extracranial radiation. 133Xe detectors for the Kety–Schmidt technique were embedded in a shielded brass block to minimize interference with radiation from the animal's body. 133Xe clearance data were analyzed using stochastic (CBF10, CBF15, and CBFINF) and initial slope methods (CBFIS), and the results were compared with CBFKS using linear regression. CBF15 and CBFINF yielded similar CBF values as CBFKS (CBFKS = 0.97 · CBF15 − 2.08, r = 0.92, p < 0.01; CBFKS = 1.13 · CBFINF − 1.21, r = 0.92, p < 0.01). CBF10 slightly overestimated CBFKS but still showed a close correlation to CBFKS (CBFKS = 0.89 · CBF10 − 2.58, r = 0.92, p < 0.01) and CBFIS considerably overestimated CBFKS (CBFKS = 0.60 · CBFIS − 1.27, r = 0.87, p < 0.01). With extracranial contamination of the 133Xe clearance curve minimized, all 133Xe clearance techniques used to measure CBF were consistently related to CBFKS in a constant, significant manner. 133Xe clearance therefore is a valid method to assess CBF during cardiopulmonary bypass.
Oxygen Consumption of the Living Human Brain Measured after a Single Inhalation of Positron Emitting Oxygen
Authors: Ohta Shinsuke , Meyer Ernst , Thompson Christopher J. , Gjedde Albert
Published: April 2011

We measured the rate of washout of 15O-labeled water generated from labeled oxygen accumulated in brain after bolus [15O]O2 inhalation, and compared the washout with that of labeled water measured with H215O. Contrary to the original expectation, the radioactive water generated from labeled oxygen failed to leave the brain tissue at the rate predicted by exogenous water. Therefore, the use of a separately measured value for exogenous water clearance led to an error in the calculation of oxygen consumption. A new method presented in this paper eliminated the error by yielding oxygen consumption in a single oxygen study. We used time-weighted integration to estimate three parameters, including the unidirectional clearance from blood to brain ( k1O2), the fractional clearance of the distribution volume in brain ( k1O2), and the vascular volume correction ( Vo). We showed that the clearance of oxygen from blood to brain can be estimated with acceptable precision by this new approach, and that the new method yields a reliable measure of oxygen consumption.
Global Cerebral Ischemia Associated with Cardiac Arrest in the Rat: I. Dynamics of Early Neuronal Changes
Authors: Kawai Kensuke , Nitecka Liliana , Ruetzler Christl A. , Nagashima Goro , Joó Ferenc , Mies Günter , Nowak Thaddeus S. , Saito Nobuhito , Lohr Julia M. , Klatzo Igor
Published: April 2011

Light microscopic neuronal changes were studied in rats subjected to 10 min of global ischemia produced by compression of the major cardiac vessels. Observations of cresyl violet-stained sections revealed early changes involving predominantly GABAergic neurons in various locations. In rats killed 15 min after recirculation, the changes were characterized by the appearance of a clear peripheral zone with condensation of the remaining neuronal cytoplasm. After 1 h, these zones appeared to be compartmentalized into individual pearl-like vacuoles, especially prominent in the nucleus reticularis thalami. After 3 h, the cytoplasmic vacuoles disappeared and the neuronal changes, particularly in the cerebral cortex, striatum, hippocampus, and pars reticulata of the substantia nigra, consisted mainly of hyperchromasia or loss of Nissl substance. After 2 days, the cerebral cortex and thalamus contained occasional neurons with conspicuously large nucleoli. After 7 days, the hippocampus revealed an approximately 50% loss of CA1 pyramidal neurons, associated with intense microglial reactivity in the stratum radiatum, whereas the neuronal destruction was more complete in the nucleus reticularis thalami. Our observations suggest a possibility that early changes in GABAergic neurons may provide a period of neuronal disinhibition and thus contribute to an excitatory ischemic damage in regions connected by GABAergic circuitry.
Tissue Pco2 in Brain Ischemia Related to Lactate Content in Normo- and Hypercapnic Rats
Authors: Katsura Kenichiro , Ekholm Anders , Siesjö Bo K.
Published: April 2011

The amount of lactate formed during ischemia determines the rise in tissue Pco2 (Ptco2). Conflicting results exist on the relationship between lactate and Ptco2. The objective of this study was to settle this issue. We varied the preischemic plasma glucose concentration of normo- and hypercapnic rats, assessed tissue lactate and total CO2 contents, and determined the Pco2/lactate relationship over the lactate range 2–40 mmol kg−1. The results showed that whatever the equilibration time, the Pco2/lactate relationship was linear. The results obtained could be reproduced by a theoretical buffer system that mimics the buffering behavior of intracellular fluid. Our results bear on the question of whether compartmentation of H+ occurs during ischemia, with glial cells becoming more acid than neurons. A discontinuous Pco2/lactate relationship, with a constant Pco2 above a certain lactate content, would support this contention. Since our results demonstrate a linear relationship between lactate and Pco2 over the lactate range 2–40 mmol kg−1, they considerably weaken any argument for gross compartmentation of H+.
The Influence of Biological and Technical Factors on the Variability of Global and Regional Brain Metabolism of 2-[18F]Fluoro-2-Deoxy-D-Glucose
Authors: Camargo Edwaldo E. , Szabo Zsolt , Links Jonathan M. , Sostre Samuel , Dannals Robert F. , Wagner Henry N.
Published: April 2011

This study investigated the influence of biological and technical factors on variations of global and regional cerebral metabolic rate of glucose (CMRglc) measured with 2-[18F]fluoro-2-deoxy-d-glucose ([18F]FDG). Twelve male volunteers (22–40 years) were investigated on three or four occasions for a total of 42 studies. We calculated the variance/covariance of the following parameters: CMRglc, six parameters of the blood clearance of [18F]FDG, hour of injection, peak time of blood radioactivity, and six components of the operational equation (nonradioactive blood glucose concentration, brain radioactivity, two integrals, numerator, and denominator). There was correlation among these six components, except for nonradioactive blood glucose. However, the correlation between the CMRglc and the individual components of the operational equation was poor. The inter- and intrapersonal CMRglc coefficients of variations were 13.8 and 7.1%, respectively. In contrast, coefficients of variations of the numerator and denominator of the operational equation were 34.6 and 32.6%, respectively, and were always in the same direction. No correlation was found between CMRglc and the technical factors in the numerator and denominator of the operational equation. Factor analysis disclosed that a single factor was responsible for 70% of the variance. This factor included caudate, putamen, thalamus, frontal cortex, temporal cortex, and cingulate gyrus. These structures are involved with multiple complex functions, from autonomic motor control to behavior and emotions. The intrinsic metabolic variability of these structures, along with the basal metabolic processes that are continuously going on in the brain, may be the best explanation for the variance encountered in our investigation.
In vivo Measurement of the Volume of Distribution of Water in Cerebral Grey Matter: Effects on the Calculation of Regional Cerebral Blood Flow
Authors: Lammertsma A. A. , Martin A. J. , Friston K. J. , Jones T.
Published: April 2011

The present study was undertaken to determine the apparent value for the volume of distribution of water to be used in the dynamic/integral technique for generating functional CBF images. A value of 0.86 resulted in only a minor loss of accuracy compared to the more accurate (but time-consuming) dynamic only analysis, which incorporated the regionally fitted estimates of the volume of distribution of water. In contrast to the traditionally used in vitro value of 0.95, the value of 0.86 allows for the inclusion of a significant part of the washout phase in the integral analysis, thereby producing statistically improved CBF images.
Improvement in Local Cerebral Blood Flow Measurement in Gerbil Brains by Prevention of Postmortem Diffusion of [14C]Iodoantipyrine
Authors: Hatakeyama Takao , Sakaki Saburo , Nakamura Ko , Furuta Shigeru , Matsuoka Kenzou
Published: April 2011

Postmortem diffusion of [14C]iodoantipyrine, which distorts the image of cerebral blood flow, can occur in at least three steps; from decapitation until the brain is frozen, while frozen sections on coverslips are thawed, and when dried sections are applied to x-ray film. In the present study, the first two steps were modified to reduce the time during which brain tissue was wet. When the brains of gerbils were taken out of the skulls and immersed in chilled isopentane (–45°C), 90–95 s elapsed between decapitation until the brain tissues were frozen. However, immersion of whole heads in liquid nitrogen after decapitation decreased the time to 25 s. The autoradiograms had better contrast after the freezing procedure with liquid nitrogen than after that with chilled isopentane. The drying time of the thawed sections was markedly reduced by blowing hot air across the sections on a hot plate, and this resulted in clearer images on autoradiograms. In most of the tissues with values of cerebral blood flow over 100 ml 100 g−1 min−1 as measured using the conventional drying method, the corresponding values were higher if the modified method was used. In contrast, in tissues with values less than 100 ml 100 g−1 min−1, the corresponding values were lower. Moreover, the differences between flows in adjacent small brain structures were less clear if the sections were dried by the conventional method. Reducing the time during which postmortem brains or sections are wet can help prevent [14C]iodoantipyrine diffusion artifacts.
Regional Imaging of Brain Tissue Calcium Ions Using Aequorin
Authors: Hashimoto Kenji , Kikuchi Haruhiko , Ishikawa Masatsune , Kobayashi Shuichi
Published: April 2011

To investigate regional changes in calcium ion concentrations, we developed a new histochemical method using aequorin, a calcium ion-sensitive photoprotein. In this method, reagent film containing aequorin was made and an unfixed slice of frozen brain 16 μm thick was placed on it. Tissue calcium ions permeated the reagent layer and the bioluminescence of aequorin-calcium ions was recorded photographically with high spatial resolution. There was a close linear relationship ( r = 0.903) between the optical density of the bioluminescent images and the logarithmic values of the tissue calcium ion concentration. Using this method, we could visualize the regional tissue calcium ion distribution in pathological states in rat brains.
Fluorescence Labeling of the Capillary Network in Rat Brains
Authors: Theilen Hermann , Kuschinsky Wolfgang
Published: April 2011

To assess the reliability of fluorescence methods for a quantitative staining of brain capillaries, three different immunohistochemical fluorescent markers were used in the rat brain. Staining of the basement membrane by antibodies directed against fibronectin was compared, in the same brain section, with simultaneous staining of the vascular endothelium constituents nonmuscle myosin or von Willebrand factor (factor VIII). These stainings all resulted in identical patterns, which demonstrates their suitability for capillary staining in the brain. It has been claimed that fixation of the tissue results in the appearance of spurious capillary spots. Such a fixation artifact could be excluded using nonmuscle myosin staining. These results validate the methods of quantitative fluorescent microscopical staining of capillary morphology in the brain and therefore support our concept of a continuous perfusion of all capillaries in the brains of conscious rats.
The Effect of MK-801 on Cortical Spreading Depression in the Penumbral Zone following Focal Ischaemia in the Rat
Authors: Gill R. , Andiné P. , Hillered L. , Persson L. , Hagberg H.
Published: April 2011

Cortical spreading depression (CSD) is a transient depression of neuronal activity that spreads across the cortical surface. In the present studies, we have investigated CSD activity in the penumbral zone following permanent middle cerebral artery (MCA) occlusion in the rat ( n = 16/group), using double-barreled Ca2+ -sensitive microelectrodes. Measurements of CSD activity were made for 3 h in each animal. During this time, a varying number of spontaneous CSDs were seen in the control group (total was 30, with a range of 0–7/rat). These CSDs were of varying duration: “small” (∼1 min) and “big” (5–45 min) CSDs. During a CSD, the extracellular [Ca2+] decreased to 0.11 ± 0.07 m M (mean ± SD). After 3 h, the extracellular [Ca2+] in the cortex (penumbral zone) was either normal (10/16 rats) or lowered to 0.5 m M (2/16 rats) or to 0.1 m M (4/16 rats). In the caudate nucleus (ischaemic core area), all rats had an extracellular [Ca2+] of ∼0.1 m M when measured after the 3 h recording period. Neuropathological evaluation of the brains of the animals, which had been allowed to survive for 24 h after MCA occlusion, revealed ischaemic damage in the dorsolateral cortex and caudate nucleus. Administration of the noncompetitive NMDA antagonist, MK-801 (3 mg/kg i.p.), 30 min after MCA occlusion resulted in 24 and 29% reductions in the volume of hemispheric and cortical damage, respectively, which was highly significant ( p < 0.0001); no protection was seen against caudate damage. MK-801 also significantly ( p < 0.05) reduced the number of CSDs (total was 10 with a range of 0–2/rat) and the degree of decrease in extracellular [Ca2+] during CSDs (low level was 0.19 ± 0.15 m M, mean ± SD). Both the number of “small CSDs” and significantly the “big CSDs” were reduced by MK-801. The “small CSDs” were present in the border zone and also deeper within the infarct, whereas “big CSDs” and anoxic depolarisations only occurred closer to the infarct core. CSDs were not seen outside the border zone of the infarct. In conclusion, there was a good correlation between extracellular [Ca2+] changes and ischaemic damage in the infarcted region following MCA occlusion. MK-801 reduced the ischaemic damage in the penumbral zone in parallel with attentuation of the number and amplitude of CSDs and thereby a reduced intracellular Ca2+ overload.
Effect of Superoxide Dismutase on Intracellular Calcium in Stroke
Authors: Araki Nobuo , Greenberg Joel H. , Uematsu Daisuke , Sladky John T. , Reivich Martin
Published: April 2011

To clarify the relationship between calcium metabolism and free radical damage during the reperfusion period following ischemia, we investigated the effect of superoxide dismutase (SOD) on changes in cytosolic free calcium, cortical blood flow, and histologic changes following focal cerebral ischemia and reperfusion in 12 cats. Using indo-1, a fluorescent intracellular Ca2+ indicator, we simultaneously measured changes in the Ca2+ signal ratio (400:500 nm), NADH signal (464 nm), and reflectance (340 nm) during ultraviolet excitation (340 nm) directly from the cortex in vivo. The middle cerebral artery (MCA) was occluded for 1 h; only cats in which the EEG amplitude was depressed to <10% of control during the occlusion were entered into the study. Starting 2 min prior to release of the occlusion and continuing for 4 min, SOD (10,000 U/kg) was slowly infused in six cats, while in six cats, the vehicle only was infused. During MCA occlusion, the Ca2+ signal ratio increased significantly in both groups with no significant difference between the groups. During reperfusion, the Ca2+ signal ratio remained at a high level in the vehicle-treated group, while in the SOD-treated group, the Ca2+ signal ratio decreased. There was a statistically significant difference between the two groups at 10, 20, and 30 min after reperfusion (p < 0.01). The histologically damaged area in the SOD-treated group was significantly smaller than that in the vehicle-treated group (p < 0.01). These data suggest that the histoprotective action of SOD may be due to its ability to attenuate increases in intracellular calcium during the recirculation period following focal cerebral ischemia.
Spontaneous Flow Oscillations in the Cerebral Cortex during Acute Changes in Mean Arterial Pressure
Authors: Hudetz Antal G. , Roman Richard J. , Harder David R.
Published: April 2011

The purpose of this study was to characterize spontaneous oscillations of blood flow in the cerebral cortex of anesthetized rats under control conditions and after mean arterial pressure was altered by various means. Blood flow was monitored using a laser–Doppler flowmeter through the closed cranium. Spontaneous flow oscillations with amplitudes of 14–30% of the mean flow and frequencies of 4–11 cycles/min were recorded when arterial pressures were less than 90 mm Hg. Stepwise hemorrhagic hypotension and unilateral carotid occlusion increased the amplitude of oscillations. The amplitude of oscillations was negatively correlated with the level of mean arterial pressure after manipulation with norepinephrine or sodium nitroprusside. The oscillations were reversibly abolished during dilation of the cerebral circulation by elevating the inspired carbon dioxide content to 5%. The frequency of flow oscillations was very stable during all of the above maneuvers except during the infusion of norepinephrine, which increased the oscillation frequency slightly. The results suggest that flow oscillations are determined primarily by cerebral arterial pressure.
Endothelium-Derived Relaxing Factor Inhibits Constrictor Responses of Large Cerebral Arteries to Serotonin
Authors: Faraci Frank M. , Heistad Donald D.
Published: April 2011

Endothelium-derived relaxing factor [EDRF, nitric oxide (NO) or a NO-containing compound] influences basal tone of cerebral blood vessels and mediates vasodilation in response to several stimuli. It is not known whether EDRF also modulates responses to cerebral vasoconstrictor stimuli in vivo. Our goal was to determine whether formation of EDRF inhibits constrictor responses of large cerebral arteries to serotonin. We measured cerebral blood flow (microspheres) and pial microvascular pressure (servo null) in anesthetized rabbits and calculated resistance of large cerebral arteries. Responses to an inhibitor of NO formation, NG-nitro-l-arginine (l-NNA, 3 mg/kg i.v.), were examined. l-NNA produced an increase in resistance of large arteries and total cerebral vascular resistance of approximately 15% (p < 0.05 for both variables) and a small decrease in cerebral blood flow (35 ± 9 vs. 32 ± 7 ml min−1 100 g−1, mean ± SD, p < 0.05). Under control conditions, infusion of serotonin (10 μg kg−1 min−1, into the left atrium) produced an increase in resistance of large arteries. Following treatment with l-NNA, the change in resistance of large arteries in response to serotonin was increased more than twofold (0.20 ± 0.17 vs. 0.43 ± 0.21 mm Hg ml−1 min 100 g, p < 0.05). In contrast, l-NNA did not alter the increase in resistance of large arteries during hypocapnia. l-arginine inhibited the effects of l-NNA on baseline cerebral vascular resistance and on responses of large arteries to serotonin. Thus, formation of EDRF (NO) from l-arginine (a) has a modest influence on cerebral blood flow under basal conditions and (b) inhibits constriction of large cerebral arteries to serotonin, but not hypocapnia.