bluuebunny/crossref_metadata_2025 huggingface dataset:
Vitamin E Uptake into the Brain and 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine Toxicity
Authors: Adams James D. , Wang Bing
Published: April 2011

The brain uptake index for vitamin E has not been reported previously. This study examined the possible involvement of altered brain vitamin E uptake as an explanation of alterations in vitamin E levels in the brain following 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration. The brain uptake index of vitamin E was evaluated in control mice and at 1 and 24 h after toxin treatment. Control mice had a brain uptake index of 6.1 ± 1.2. The toxin induced more than a twofold increase in the vitamin E brain uptake index to 15.2 ± 6.8 at 1 h after treatment, which returned to control values at 24 h. The dramatic increase in the brain uptake index of vitamin E may explain the increases in vitamin E levels found in some brain regions following MPTP administration.
Temperature Dependent Change of Apparent Diffusion Coefficient of Water in Normal and Ischemic Brain of Rats
Authors: Hasegawa Yasuhiro , Latour Lawrence L. , Sotak Christopher H. , Dardzinski Bernard J. , Fisher Marc
Published: April 2011

To identify the temperature dependent change of the apparent diffusion coefficient (ADC) of water in brain tissue, the ADC values of normal rat brain were measured over a range of body temperatures with monitoring of head temperature using a small water reference implanted under the temporalis muscle. An initial experiment using thermocouples implanted into the cortex, caudate-putamen, temporalis muscle, and rectum demonstrated that temperature in all regions were highly correlated over a temperature range from 33 to 39°C. In another group of normal rats, brain ADC values varied almost uniformly with body temperature over the temperature range 33–39°C, implying that brain ADC values accurately reflect changes in brain temperature. The effects of focal ischemia and administration of the noncompetitive N-methyl-d-aspartate (NMDA) antagonist, CNS-1102, on ADC were also examined, using the suture middle cerebral artery (MCA) occlusion model while maintaining the body temperature at 37°C. ADC values and therefore brain temperature in the nonischemic and ischemic hemispheres were not affected by the drug. These experiments suggest that brain ADC measurement could be useful in animal studies and, potentially, in humans to assess the effects of pharmacologic intervention on brain temperature.
In vivo Binding of [3H]Nimodipine in Rat Brain after Transient Forebrain Ischemia
Authors: Takizawa Shunya , Hogan Matthew J. , Buchan Alastair M. , Hakim Antoine M.
Published: April 2011

We report the regional variation in relative in vivo binding of the l-type voltage sensitive calcium channel (VSCC) antagonist [3H]nimodipine to brain following transient forebrain ischemia in the rat. At 30-min of reperfusion after 20 min of forebrain ischemia, [3H]nimodipine binding was significantly increased in striatum, CA3 and CA4, and dentate relative to binding in sham-operated rats, suggesting that VSCCs were responding to ischemic depolarization. Two h following ischemia, binding in all brain structures returned to normal levels indicating repolarization of cell membranes. At 24 h of recirculation, increased [3H]nimodipine binding was again observed in striatum and dentate. Binding remained elevated in the striatum and dentate, and increased binding became evident in the CA1 region of the hippocampus after 48 h of reperfusion. With the exception of the dentate gyrus, the second rise in [3H]nimodipine binding anticipated or coincided with the observed regional ischemic cell changes. These observations in global cerebral ischemia support previous work indicating that in vivo binding of [3H]nimodipine to the l-type VSCC may be an early and sensitive indicator of impending ischemic injury. Such measurements may be of use in identifying vulnerable brain regions and defining a therapeutic window of opportunity in models of cerebral ischemia.
Activation of Regional Cerebral Blood Flow by a Memorization Task in Early Parkinson's Disease Patients and Normal Subjects
Authors: Démonet J.-F. , Celsis P. , Agniel A. , Cardebat D. , Rascol O. , Marc-Vergnes J.-P.
Published: April 2011

Task-induced changes in regional cerebral blood flow (rCBF) during memory activation were compared in 18 right-handed patients with early Parkinson's disease (PD) and 20 normal volunteers using the same activation paradigm. We used single-photon emission computed tomography and 133Xe in 21 regions of interest during rest, passive listening of a word list, and memorization of another word list, which was followed by a free recall test immediately after completion of the rCBF measurement. The average performance on free recall was not significantly lower in PD patients than in controls. In normal subjects, five left-sided regions (anterior middle frontal, posterior inferior frontal, superior middle temporal, thalamic, and lenticular) showed a significant increase in memorizing compared to passive listening. This pattern of activation suggests the existence of a verbal rehearsal strategy during the memorization task in normals. In PD patients, increases in these regions did not reach significance, whereas significant activations were noted in superior prefrontal regions. Such alterations in the pattern of activation in PD patients, despite a memory performance similar to that of controls are viewed as a consequence of an early dysfunction of the articulatory loop system and of compensatory mechanisms in other parts of the frontal lobe emerging in the early stages of the disease.
Nitric Oxide and Prostanoids Participate in Cerebral Vasodilation Elicited by Electrical Stimulation of the Rostral Ventrolateral Medulla
Authors: Golanov Eugene V. , Reis Donald J.
Published: April 2011

We investigated, using laser-Doppler flowmetry, whether nitric oxide (NO)- and/or indomethacin (IND)-sensitive mechanisms mediate the elevations of regional cerebral blood flow (rCBF) elicited by electrical stimulation of the rostral ventrolateral medulla (RVL) in the anesthetized spinalized rat. Stimulation of the RVL for 10 s caused increased rCBF in the frontal cortex by 31% ( n = 46), peaking at 22 s and persisting for up to 8 min. Intravenous l-nitro- NG-arginine (NNA) dose dependently and reversibly increased arterial pressure and reduced basal and evoked rCBF to 74 and 54% of the control, respectively ( p < 0.05; n = 7). Superfused over the cortex, NNA dose dependently reduced only the evoked elevations of rCBF, to 39% of the control ( p < 0.05; n = 6). Intravenous IND decreased the basal rCBF dose dependently and decreased the elevations evoked from the RVL by 38% ( p < 0.05), but IND was without effect when superfused. Combined, the effects of intravenous NNA and IND summated, reducing rCBF by 70%. However, when NNA and IND were superfused together, the inhibition of the evoked vasodilation was comparable to that elicited by NNA alone. We conclude that the elevation in rCBF elicited from the RVL is partially mediated by (a) NO synthesized locally in the cortex in response to an afferent neural signal and (b) an IND-sensitive mechanism, probably a product of cyclooxygenase, located in larger cerebral arteries, in response to a retrograde vascular signal resulting from increased blood flow within the brain.
Role of Nitric Oxide in Regulating Cerebrocortical Oxygen Consumption and Blood Flow during Hypercapnia
Authors: Horvath Ildiko , Sandor Norbert T. , Ruttner Zoltan , McLaughlin Alan C.
Published: April 2011

The effect of the nitric oxide (NO) synthase inhibitor Nω-nitro-l-arginine methyl ester (l-NAME) on the response of cerebrocortical oxygen consumption (CMRO2) and blood flow (CBF) to two levels of hypercapnia (Paco2 ∼ 60 mm Hg and Paco2 ∼ 90 mm Hg) was investigated in ketamine-anesthetized rats. CBF was calculated using the Kety–Schmidt approach and CMRO2 was calculated from the product of CBF and the arteriovenous (superior sagittal sinus) difference for oxygen. l-NAME treatment did not have a significant effect on either CMRO2 or CBE under normocapnic conditions but inhibited the hypercapnic increase of CMRO2 and the hypercapnic increase in CBF. These results suggest that NO plays a role in the response of CMRO2 and CBF during hypercapnia and are consistent with the suggestion that at least part of the increase in CBF observed during hypercapnia is coupled to an increase in CMRO2.
Pharmacologic Reversal of Acute Changes in Diffusion-Weighted Magnetic Resonance Imaging in Focal Cerebral Ischemia
Authors: Lo Eng H. , Matsumoto Keigo , Pierce Allen R. , Garrido Leoncio , Luttinger Daniel
Published: April 2011

Recently, diffusion-weighted magnetic resonance imaging (DWI) has been shown to visualize acute ischemic lesions in the brain before changes are observable with conventional magnetic resonance imaging. However, the underlying mechanisms of these acute DWI changes are unclear and may include both reversible and irreversible damage. In this study, we demonstrate that acute DWI lesions may be reversed with MK801 therapy postischemia. Sprague–Dawley rats (n = 12) were subjected to middle cerebral artery occlusion and DWI scans were obtained beginning 60 min postocclusion. Distinct regions of hyperintensity were observed in the basal ganglia and cortex, corresponding with the expected distribution of ischemia in this model. After the first scan, animals were treated with MK801 (0.5 mg/kg i.v.) or normal saline and subsequently scanned again 30 and 60 min after treatment. In the control group, the area of hyper-intense lesions continued to increase, by 55% in the cortex and 57% in the basal ganglia. MK801 therapy significantly (p < 0.01) reduced the area of damage by the third DWI scan at 60 min posttreatment (– 50% cortex, −22% basal ganglia, −41% total hemisphere) compared to pretreatment scans. Tetrazolium (TTC) stains at 24 h confirmed that MK801 significantly reduced the volumes of infarction (p < 0.05). These results demonstrate that significant portions of the acute ischemic lesion on DWI are reversible with pharmacologic intervention.
Dynamic Magnetic Resonance Imaging of the Rat Brain during Forepaw Stimulation
Authors: Hyder Fahmeed , Behar Kevin L. , Martin Margaret A. , Blamire Andrew M. , Shulman Robert G.
Published: April 2011

A magnetic resonance (MR) imaging brain mapping method was used to localize an activated volume of brain tissue in chloralose-anesthetized rats during electrical stimulation of the forepaw. Physiologically-induced changes are characterized by alterations of the magnetic properties of blood as determined by the oxygenation state of hemoglobin. Stimulation of the left forepaw led to an increase in MR signal intensity of the contralateral frontal and parietal cortices, which corresponded to forelimb motor and somatosensory areas. The activation was contiguous in coronal planes between +5 and +2 mm anterior to the bregma, and its volume was calculated to be 20–30 mm3. Each activated region was revealed using a paired t-test statistical analysis method and the activated volume was calculated from regions exposed by thresholding at p < 0.005. Physiologically-induced fractional signal changes, ΔS/S, in the motor and somatosensory areas were 0.06 ± 0.04 and 0.17 ± 0.06, respectively.
An Ultrasonic Doppler Venous Outflow Method for the Continuous Measurement of Cerebral Blood Flow in Conscious Sheep
Authors: Upton Richard , Grant Cliff , Ludbrook Guy
Published: April 2011

A pulsed ultrasonic Doppler venous outflow method was developed for the continuous measurement of global cerebral blood flow (CBF) in conscious sheep. The sheep were prepared under anesthesia with a “suture down”-style ultrasonic flow probe on the dorsal sagittal sinus placed via a trephine hole. Angiographic and dye studies showed that the dorsal sagittal sinus at the point of placement of the probe collected the majority of the blood from the cerebral hemispheres. Studies of the blood velocity profile across the sinus showed that the dimensions of the dorsal sagittal sinus changed minimally with changes in CBF in vivo. The velocity measurements were calibrated under anesthesia against an in vivo direct venous outflow method. Control CBF values for six sheep ranged from 31 to 53 ml/min for the area of brain described above; for two sheep in which the weight of the brain was determined, this gave total CBF values of approximately 34 and 30 ml min−1 100 g−1. The CBF measured varied in the expected manner with changes in the end-tidal CO2 concentration in expired breath and showed transient reductions with the barbiturate thiopentone and transient increases with the opiate alfentanil. It is concluded that the method is simple and accurate.
Brain-Derived Neurotrophic Factor Protects against Ischemic Cell Damage in Rat Hippocampus
Authors: Beck Thomas , Lindholm Dan , Castrén Eero , Wree Andreas
Published: April 2011

The neuroprotective action of brain-derived neurotrophic factor (BDNF) was evaluated in a rat model of transient forebrain ischemia. A continuous intraventricular infusion of BDNF for 7 days starting immediately before the onset of ischemia significantly increased the number of pyramidal cells in the vulnerable CA1 sector of the hippocampus. In situ hybridization experiments suggest the neuroprotection to be mediated via trkB – receptors in the hippocampus. The data indicate a therapeutic potential for the treatment of cerebral ischemia.
4-Hydroxynonenal, a Lipid Peroxidation Product, Induces Relaxation of Human Cerebral Arteries
Authors: Martínez M. Carmen , Bosch-Morell Francisco , Raya Ángel , Romá Joaquín , Aldasoro Martín , Vila José , Lluch Salvador , Romero Francisco J.
Published: April 2011

The relaxant effect of 4-hydroxynonenal (4-HNE), a lipid peroxidation product, on human cerebral arteries was studied. Addition of 4-HNE to artery rings promoted no contraction, and after stimulation with prostaglandin F2α (PFG2α; 10−7-3 × 10−6 M), 100% relaxation was obtained with 3 × 10−5 M 4-HNE. Inhibition of nitric oxide formation with NG-nitro-l-arginine methyl ester hydrochloride (l-NAME; (10−4 M), as well as prostaglandin synthesis with indomethacin (3 × 10−6 M), partially prevented 4-HNE-induced relaxation, but each of these substances separately failed to inhibit complete relaxation. Addition of both inhibitors together reduced 4-HNE-induced relaxation to ≈50%, but relaxation could not be abolished. When the endothelium was removed, 4-HNE did not promote relaxation after PGF2α stimulation. The possible roles of different intracellular signaling systems in the vascular effect of 4-HNE are discussed.
Imaging Transient, Randomly Occurring Neuropsychological Events in Single Subjects with Positron Emission Tomography: An Event-Related Count Rate Correlational Analysis
Authors: Silbersweig David A. , Stern Emily , Schnorr Leonard , Frith Christopher D. , Ashburner John , Cahill Connie , Frackowiak Richard S. J. , Jones Terry
Published: April 2011

Many neuropsychiatric symptom states are idiosyncratic, involuntary, randomly occurring, subjective, and transient. The brain states associated with these clinically important mental states cannot be imaged directly with existing positron emission tomography (PET) techniques. A new PET method that brings such mental/brain states under experimental control for analysis in single subjects is described. It utilizes a slow bolus H215O three-dimensional (3D) regional CBF imaging technique. The analysis focuses upon natural or experimentally induced variance in the temporal distribution of specific neuropsychological events over the course of a study session. For each scan, the amount of radioactivity entering the brain during these events is calculated to derive a score reflecting the contribution of the events to the image. A statistical analysis is then performed to identify those pixels in which the intensity covaries with the scan scores over the subject's scans. This permits the identification of the brain areas associated with the mental state of interest. The method is validated using an auditory sentence-monitoring task. The detection in single subjects of cerebral activations associated with recurrent events as brief as 2 s in duration is demonstrated. This method may be used as a means of imaging ephemeral neurologic or neuropsychiatric symptom states or as an alternative to a subtraction design for activation studies.
Positron Emission Tomography of 5-HT Transporter Sites in the Baboon Brain with [11C]McN5652
Authors: Szabo Zsolt , Scheffel Ursula , Suehiro Makiko , Dannals Robert F. , Kim Sang Eun , Ravert Hayden T. , Ricaurte George A. , Wagner Henry N.
Published: April 2011

[C]McN5652 is a new radioligand specific for 5-hydroxytryptamine (5-HT; serotonin) transporters. In this study we used [11C]McN5652 to image the 5-HT transporter sites in baboon brain by positron emission tomography (PET). Dynamic PET studies were performed in three Papio anubis baboons. The animals were injected intravenously first with 11C-labeled (+)-McN5652([11C](+)McN5652), then with pharmacologically inactive enantiomer 11C-labeled (–)-McN5652 ([11C](–)McN5652); two animals received a third study with [11C](+)McN5652 after pretreatment with the specific 5-HT uptake site inhibitor fluoxetine (5 mg/kg). Initial uptake into the brain was similar for both [11C](+)McN5652 and [11C](–)McN5652. At later times (45–120 min after injection), only [11C](+)McN5652 showed a distribution characteristic for 5-HT uptake sites. In contrast, in studies with [11C](–)McN5652 and in those with [11C](+)McN5652 after 5-HT uptake site blockade with fluoxetine, 11C radioactivity concentrations were significantly lower and the distribution pattern was relatively even. The differences between [11C](+)-and (–)McN5652 were calculated for the time interval 95–125 min postinjection and used to estimate specific binding. Specific binding correlated well ( r = 0.95, p < 0.001) with the known density of 5-HT uptake sites in human brain. These results indicate that [11C](+)McN5652 is suitable for PET imaging of 5-HT uptake sites in primate brain.
Delayed Treatment with Intravenous Basic Fibroblast Growth Factor Reduces Infarct Size following Permanent Focal Cerebral Ischemia in Rats
Authors: Fisher Marc , Meadows Mary-Ellen , Do Tuyen , Weise Jens , Trubetskoy Vladimir , Charette Marc , Finklestein Seth P.
Published: April 2011

Basic fibroblast growth factor (bFGF) is a polypeptide that supports the survival of brain cells (including neurons, glia, and endothelia) and protects neurons against a number of toxins and insults in vitro. This factor is also a potent dilator of cerebral pial arterioles in vivo. In previous studies, we found that intraventricularly administered bFGF reduced infarct volume in a model of focal cerebral ischemia in rats. In the current study, bFGF (45 μg/kg/h) in vehicle, or vehicle alone, was infused intravenously for 3 h, beginning at 30 min after permanent middle cerebral artery occlusion by intraluminal suture in mature Sprague–Dawley rats. After 24 h, neurological deficit (as assessed by a 0- to 5-point scale, with 5 = most severe) was 2.6 ± 1.0 in vehicle-treated and 1.5 ± 1.3 in bFGF-treated rats (mean ± SD; TV = 12 vs. 11; p = 0.009). Infarct volume was 297 ± 65 mm3 in vehicle- and 143 ± 135 mm3 in bFGF-treated animals ( p = 0.002). During infusion, there was a modest decrease in mean arterial blood pressure but no changes in arterial blood gases or core or brain temperature in bFGF-treated rats. Autoradiography following intravenous administration of 111In-labeled bFGF showed that labeled bFGF crossed the damaged blood–brain barrier to enter the ischemic (but not the nonischemic) hemisphere. Whether the infarct-reducing effects of bFGF depend on intraparenchymal or intravascular mechanisms requires further study.
Graded Hypotension and MCA Occlusion Duration: Effect in Transient Focal Ischemia
Authors: Zhu Chang Z. , Auer Roland N.
Published: April 2011

The first 2 h of middle cerebral artery occlusion (MCAO) are likely critical in determining the final outcome in ischemic stroke. To study this early postischemic period, male Wistar rats ( n = 161) were subjected to right MCAO with closely spaced step variations in both duration of MCAO and blood pressure (BP), using the intraluminal suture technique. Quantitative neuropathology was performed at 25 coronal planes of the brain after 1-week survival. Atrophy was measured as the difference between the two hemispheres and was added to cortical and striatal necrosis to obtain total tissue loss. Damage consistently increased monotonically with increasing duration of occlusion only when infarct size was expressed as percentage of the contralateral hemisphere, but not when expressed as mm3, because of variable tissue size. The results showed that already at 1 week, the quantity of tissue loss due to resorption and transsynaptic effects approached the quantity of geographically traceable necrosis in cortex and striatum. Minimum brain damage (5%) occurred after 60 min at a BP of 80 mm Hg, with almost no cortical necrosis. Damage was extremely sensitive to hypotension and MCAO duration. At a BP of 40 mm Hg, 60 min of MCAO produced 25% damage, accelerating every 20 min during the 2-h period studied. At BP 80 mm Hg, 120 min of MCAO produced the same damage as only 80 min of MCAO at BP 60 mm Hg. At 60-, 80-, 100-, and 120-min duration of MCAO, infarct size was significantly reduced with increasing BP. Analysis of the independent contribution of BP and MCAO duration revealed that BP played a greater role in determining infarct size than did MCAO duration. Ipsilateral hippocampal damage was seen in CA1 and, in some animals, CA3. Necrotic neurons in hippocampus were found in 21 animals, including four with bilateral hippocampal damage, largely but not exclusively distributed in the hypotensive groups. Contralateral necrotizing damage was seen in cortex and hippocampus as selective neuronal necrosis and as cortical infarction in two animals. Ipsilateral and contralateral hippocampal damage reproduced the pattern of selective vulnerability seen in global ischemia. The histologic penumbra (rim of selective neuronal necrosis surrounding the infarct) increased over time at BP 80 mm Hg but remained constant at a larger, presumably maximal level at BP 40 mm Hg in spite of increasing infarct size. We conclude that the first 2 h after MCAO is a very dynamic period, with increasing infarct size every 20 min, a process extremely sensitive to hypotension during occlusion. Transsynaptic effects can produce necrotizing damage in the hemisphere opposite to the ischemia.
Long-Term Spatial Cognitive Impairment after Middle Cerebral Artery Occlusion in Rats: No Involvement of the Hippocampus
Authors: Okada Mitsuko , Nakanishi Hiroshi , Tamura Akira , Urae Akinori , Mine Kazunori , Yamamoto Kenji , Fujiwara Michihiro
Published: April 2011

The behavioral and neurochemical 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 to solve a radial eight-arm maze task during an entire 1-month period, whereas seven rats were able to solve this task. Three months after occlusion, 19 MCA-occluded rats failed to solve the task successfully again for at least 1 month (the cognitively impaired rats), whereas 11 MCA-occluded rats were able to solve it (the cognitively unimpaired rats). The rats that underwent behavioral testing were examined for any changes in the acetylcholine (ACh) levels in the hippocampus using HPLC with electrochemical detection or the formation of long-term potentiation (LTP) in the population spike of the hippocampal CA1 field. The immunohistochemical distribution of either the microtubule-associated protein 2 (MAP2) or glial fibrillary acidic protein (GFAP) in the hippocampus of the cognitively impaired rats was also studied. In the cognitively impaired rats, neither the suppression of the induction of LTP, nor the degradation of MAP2, nor the increase in the GFAP immunoreactivity was observed in the hippocampus. The levels of ACh in the hippocampus did not change significantly among the cognitively impaired, unimpaired, and the sham-operated rats. These results suggest that MCA occlusion is capable of producing long-term spatial cognitive disturbance in rats without any evidence of neurobiological damage in the hippocampus.
Cerebral Blood Flow and Metabolic Responses to Sustained Hypercapnia in Awake Sheep
Authors: Yang Shih-Ping , Krasney John A.
Published: April 2011

This investigation determined the effects of sustained hypercapnia on cerebral blood flow (CBF; radiolabeled microspheres), cerebral metabolic rates for O2 and glucose (CMRO2 and CMRglc), and brain water content in conscious sheep instrumented with aortic, left ventricular, vena cava, and brain sagittal sinus catheters. PaCO2 was elevated from 38 ± 3 to 53 ± 3 (mean ± SD) mm Hg and PaO2 from 109 ± 7 to 131 ± 4 mm Hg for 96 h in an environmental chamber. Hypercapnia did not alter sheep behavior, food and water intake, arterial pressures, core temperature, or brain lactate release. Total and regional CBF and CBF/CMRO2 reached peak values at 1 h and then readjusted, to stabilize at lower, but still elevated levels at 24 h and thereafter. CMRO2 and CMRglc increased at 6 h and thereafter during hypercapnia. PaCO2, CBF, CMRO2, and CMRglc remained elevated at 3 h after restoration to room air, while CBF/CMRO2 returned to the control value. Frontal and occipital lobe wet-to-dry weight ratios increased modestly but significantly after hypercapnic exposure. It is concluded that sustained hypercapnia induces stable and nonadapting increases in both CBF and brain metabolism that persist for at least 3 h after restoration to room air in association with hypoventilization and modest elevations of brain water.
Benzodiazepine Receptor Quantification in vivo in Humans Using [11C]Flumazenil and PET: Application of the Steady-State Principle
Authors: Lassen N. A. , Bartenstein P. A. , Lammertsma A. A. , Prevett M. C. , Turton D. R. , Luthra S. K. , Osman S. , Bloomfield P. M. , Jones T. , Patsalos P. N. , O'Connell M. T. , Duncan J. S. , Andersen J. Vanggaard
Published: April 2011

Carbon-11-labeled flumazenil combined with positron emission tomography (PET) was used to measure the concentration ( Bmax) of the benzodiazepine (Bz) receptor in the brain and its equilibrium dissociation constant ( KD) for flumazenil in five normal subjects. The steady-state approach was used injecting the tracer as a bolus of high specific activity. In each subject two studies were carried out. The first study was performed at essentially zero receptor occupancy, the tracer alone study. The second study was performed at a steady-state receptor occupancy of about 50%, achieved by a prolonged constant infusion of nonlabeled (“cold”) flumazenil starting 2 h before the bolus tracer injection and continuing until the end of the scanning period. In this second study the free concentration of unmetabolized flumazenil in plasma water was measured in multiple blood samples. The observed tissue and plasma tracer curves, calibrated in the same units of radioactivity per millimeter, were analyzed in two ways: (a) by the noncompartmental (stochastic) approach making no assumptions regarding number of compartments in the tissue, and (b) by the single-compartment approach assuming rapid exchange (mixing) of tracer between all tissue compartments. The noncompartmental and the compartmental analyses gave essentially the same values for the distribution volume of the tracer, the parameter used for quantitation of the Bz receptor. As the compartmental approach could be applied to a shorter observation period (60 min instead of 120 min) it was preferred. The five subjects had a mean KD value of 12 n M/L of water and Bmax values of the grey matter ranging from 39 ± 11 in thalamus to 120 ± 14 n M/L of brain in occipital cortex. Most previous studies have been based on the pseudoequilibrium approach using the brain stem as a receptor-free reference region. This yields practically the same KD but lower Bmax values than the steady-state approach presented here.
In vivo Detection of Superoxide Anion Production by the Brain Using a Cytochrome c Electrode
Authors: Fabian Roderic H. , DeWitt Douglas S. , Kent Thomas A.
Published: April 2011

A cytochrome c-coated platinized carbon electrode was utilized to detect superoxide generated by the brain during hypoxia/hypercarbia, focal ischemia, and reperfusion and following fluid percussion brain injury with and without hemorrhagic hypotension and reperfusion in the rat. All three of these forms of brain injury were associated with an increase in the superoxide signal. The cytochrome c electrode proved to be sensitive and responsive enough for minute-by-minute measurement of superoxide generation by brain tissue.
Systemic and Cerebral Kinetics of 16α[18F]Fluoro-17β-Estradiol: A Ligand for the in vivo Assessment of Estrogen Receptor Binding Parameters
Authors: Moresco R. M. , Casati R. , Lucignani G. , Carpinelli A. , Schmidt K. , Todde S. , Colombo F. , Fazio F.
Published: April 2011

Estrogen receptors are expressed in several brain areas of various animal species, and steroid hormones exert physiologic and biochemical effects on the central nervous system. The aim of the present study was to evaluate in female adult rats, the suitability of 16α[18F]fluoro-17β-estradiol ([18F]FES), a selective estrogen receptor ligand, for the in vivo assessment of brain estrogen receptors. This was considered to be a preliminary step in evaluating the potential usefulness of [18F]FES for studies of cerebral estrogen receptors with positron emission tomography (PET) in nonhuman primates and human subjects. We evaluated (a) the time course of the metabolic degradation of [18F]FES in blood; (b) the time course of distribution of the tracer in discrete cerebral areas; (c) the inhibitory effect of increasing doses of cold estradiol on cerebral [18F]FES uptake; and (d) the possibility of in vivo quantification of estrogen receptor binding parameters using both equilibrium and dynamic kinetic analyses. We quantified [18F]FES binding to estrogen receptors using both equilibrium and dynamic kinetic analyses. The results of this study indicate that [18F]FES is a suitable tracer for the measurement of estrogen receptors in the pituitary and hypothalamus, using either the equilibrium or the kinetic analysis. However, [18F]FES is inadequate for the in vivo investigation of estrogen binding sites in brain areas with low receptor density, such as the hippocampus.
Simultaneous Measurement of Cerebral Oxygen Consumption and Blood Flow Using 17O and 19F Magnetic Resonance Imaging
Authors: Pekar James , Sinnwell Teresa , Ligeti Laszlo , Chesnick A. Scott , Frank Joseph A. , McLaughlin Alan C.
Published: April 2011

17O and 19F magnetic resonance (MR) imaging were used to determine simultaneously the concentrations of H217O and CHF3 in 0.8-cc voxels in the cat brain during inhalation of a gas mixture containing both 17O2 and CHF3. The arterial time course of CHF3 was determined by “on-line” mass spectrometer detection of expired CHF3, and the arterial time course of H217O was determined by 17O MR analysis of arterial samples withdrawn during the inhalation period. The brain data and the arterial data for the two tracers were combined to calculate the cerebral oxygen consumption (CMRO2) and the CBF. The protocol was repeated on seven cats, using pentobarbital anesthesia. The average values of CMRO2 and CBF for a 0.8-cc voxel in the parietal cortex were 1.5 ± 0.5 mmol kg−1 min−1 and 38 ± 15 ml 100 g−1 min−1, respectively. In individual animals the average uncertainty in CMRO2 and CBF, calculated from Monte Carlo approaches, was ±9%.
Commentary and Opinion: I. Principal Component Analysis, Variance Partitioning, and “Functional Connectivity”
Authors: Strother Stephen C. , Kanno Iwao , Rottenberg David A.
Published: April 2011

We briefly review the need for careful study of “variance partitioning” and “optimal model selection” in functional positron emission tomography (PET) data analysis, emphasizing the use of principal component analysis (PCA) and the importance of data analytic techniques that allow for heterogeneous spatial covariance structures. Using an [15O]water dataset, we demonstrate that—even after data processing—the intrasubject signal component of primary interest in baseline activation studies constitutes a very small fraction of the intersubject variance. This small intrasubject variance component is subtly but significantly changed by using analysis of covariance instead of scaled subprofile model processing before applying PCA. Finally, we argue that the concept of “functional connectivity” should be interpreted very generally until the relative roles of inter- and intrasubject variability in both disease and normal PET datasets are better understood.
Early Endonuclease Activation following Reversible Focal Ischemia in the Rat Brain
Authors: Charriaut-Marlangue C. , Margaill I. , Plotkine M. , Ben-Ari Y.
Published: April 2011

The structural changes that occur in chromatin DNA after ischemic brain injury are poorly understood. The presence of oligonucleosome fragments that are recognized as the characteristic DNA ladder has been demonstrated in global and focal ischemia, associated or not with random DNA fragmentation. Using pulsed-field gel electrophoresis, which improves DNA separation, we have now detected initial stages of DNA fragmentation that occur already 6 h after reversible focal cerebral ischemia in rats. This result confirms that internucleosomal DNA fragmentation precedes random DNA fragmentation in vulnerable striatal and cortical neurons following reversible focal cerebral ischemia.
Analysis of Time Courses of Metabolic Precursors and Products in Heterogeneous Rat Brain Tissue: Limitations of Kinetic Modeling for Predictions of Intracompartmental Concentrations from Total Tissue Activity
Authors: Schmidt Kathleen C. , Mies Günter , Dienel Gerald A. , Cruz Nancy F. , Crane Alison M. , Sokoloff Louis
Published: April 2011

The efficacy of various kinetic models to predict time courses of total radioactivity and levels of precursor and metabolic products was evaluated in heterogeneous samples of freeze-blown brain of rats administered [14C]deoxyglucose ([14C]DG). Two kinetic models designed for homogeneous tissues, i.e., a no-product-loss, three-rate-constant (3K) model and a first-order-product-loss, four-rate-constant (4K) model, and a third kinetic model designed for heterogeneous tissues without product loss [Tissue Heterogeneity (TH) Model] were examined. In the 45-min interval following a pulse of [14C]DG, the fit of the TH Model to total tissue radioactivity was not statistically significantly better than that of the 3K Model, yet the TH Model described the time courses of [14C]DG and its metabolites more accurately. The TH- and 4K-Model-predicted time courses of [14C]DG and its metabolites were similar. Whole-brain glucose utilization (CMRglc) calculated with the TH or 3K Model, ∼75 μmol 100 g−1 min−1, was similar to values previously determined by model-independent techniques, whereas CMRglc calculated with the 4K Model was 44% higher. In a separate group of rats administered a programmed infusion to attain a constant arterial concentration of [14C]DG that minimizes effects of tissue heterogeneity as well as any product loss, CMRglc calculated with all three models was 79 μmol 100 g−1 min−1 at 45 min after initiation of the infusion. Statistical comparisons of goodness of fit of total tissue radioactivity were, therefore, not indicative of which models best describe the tissue precursor and product pools or which models provide the most accurate rates of glucose utilization.
Evidence That Acetylcholine Mediates Increased Cerebral Blood Flow Velocity in Crucian Carp through a Nitric Oxide—Dependent Mechanism
Authors: Hylland Patrick , Nilsson Göran E.
Published: April 2011

Nitric oxide (NO)–dependent regulation of brain blood flow has not been proven to exist in fish or other ectothermic vertebrates. Using epi-illumination microscopy on the brain surface (optic lobes) of crucian carp ( Carassius carassius), we show that superfusing the brain with acetylcholine (ACh) induces an increase in cerebral blood flow velocity that can be completely blocked by the NO synthase inhibitors NG-nitro-l-arginine methylester (L-NAME) and NG-nitro-l-arginine. Also, sodium nitroprusside, which decomposes to liberate NO, causes an increase in cerebral blood flow velocity. By contrast, L-NAME does not block the increase in blood flow velocity caused by anoxia. The results suggest that NO is an endogenous vasodilator in crucian carp brain that mediates the effects of ACh. Because teleost fish deviated from other vertebrates 400 million years ago, these results suggest that NO-dependent brain blood flow regulation was an early event in vertebrate evolution.
The Contribution of δ1- and δ2-Opioid Receptors to Hypoxia-Induced Pial Artery Dilation in the Newborn Pig
Authors: Armstead W. M.
Published: April 2011

Previously, it has been observed that μ-opioid receptors contribute to while κ-opioid receptors oppose pial artery dilation in response to hypoxia. The present study was designed to investigate the contribution of δ1- and δ2-opioid receptor activation to hypoxia-induced pial vasodilation. Newborn pigs equipped with a closed cranial window were used to measure pial artery diameter and collect cortical periarachnoid CSF for assay of opioids. Hypoxia increased CSF leucine enkephalin (a δ-agonist) from 36 ± 6 to 113 ± 17 pg/ml (n = 5). Hypoxiainduced pial artery vasodilation was attenuated during moderate hypoxia (Pao2 ≈ 35 mm Hg), while this response was blunted during severe hypoxia (Pao2 ≈ 25 mm Hg), by the δ1-opioid receptor antagonist 7-benzylidenenaltrexone (BNTX; 10−8 M) (23 ± 2 vs. 13 ± 2 and 34 ± 6 vs. 10 ± 3% for moderate and severe hypoxia in the absence and presence of BNTX, respectively; n = 5). In contrast, the δ2-opioid receptor antagonist naltrindole (10−9 M) blunted pial vasodilation during moderate hypoxia, but only attenuated the vasodilator response during severe hypoxia (22 ± 2 vs. 8 ± 2 and 33 ± 4 vs. 23 ± 4% for moderate and severe hypoxia in the absence and presence of naltrindole, respectively; n = 5). Receptor selectivity experiments show that BNTX blocked responses to the δ1-agonist DPDPE, whereas responses to the δ2-agonist deltorphin II were unchanged (12 ± 3 vs. 2 ± 1% and 14 ± 4 vs. 14 ± 3% for DPDPE at 10−6 M and deltorphin II at 10−6 M in the absence and presence of BNTX; n = 5). Similarly, naltrindole blocked responses to deltorphin II, but responses to DPDPE were unchanged. These data indicate that δ1-receptor activation contributes to both moderate and severe hypoxia-induced vasodilation, but the δ1-receptors appear to be more important during severe hypoxia relative to δ2-receptors. Additionally, these data show that δ2-receptors primarily contribute to dilation during moderate hypoxia.
Immunohistochemical Localization of Superoxide Dismutase in the Hippocampus following Ischemia in a Gerbil Model of Ischemic Tolerance
Authors: Kato Hiroyuki , Kogure Kyuya , Araki Tsutomu , Liu Xiao-Hong , Kato Kanefusa , Itoyama Yasuto
Published: April 2011

Pretreatment of the gerbil brain with a 2-min period of sublethal ischemia protects against neuronal damage following a subsequent 3-min period of ischemia, which normally destroys pyramidal neurons in the CA1 region of the hippocampus. To clarify the role of superoxide dismutase (SOD) in this ischemic tolerance, we immunohistochemically investigated the alterations in copper-zinc SOD (CuZnSOD) and manganese SOD (MnSOD) in the gerbil hippocampus following 3-min ischemia with or without the first mild ischemia. Normal hippocampus showed an intense CuZnSOD immunostaining in pyramidal neurons but relatively less MnSOD immunostaining. MnSOD, but not CuZnSOD, immunoreactivity increased after the first ischemia. Both CuZnSOD and MnSOD immunoreactivities decreased throughout the hippocampus 4 h after 3 min of ischemia both with and without the first ischemia. The immunostaining recovered in resistant regions (CA3 and dentate gyrus) after 1 day in both groups and in the pretreated CA, after 2 days. Without pretreatment, however, the immunostaining never recovered in the vulnerable CA, region. The results suggest that ischemic tolerance is induced in part by enhanced synthesis of MnSOD in the tolerance-acquired hippocampus. Both CuZnSOD and MnSOD immunoreactivities decreased after the second ischemia even in the pretreated hippocampus in the early reperfusion periods, but ischemic tolerance facilitated the recovery from the postischemic reductions in SOD immunoreactivity.
Identification of Collaterally Perfused Areas following Focal Cerebral Ischemia in the Rat by Comparison of Gradient Echo and Diffusion-Weighted MRI
Authors: Roussel S. A. , van Bruggen N. , King M. D. , Gadian D. G.
Published: April 2011

Diffusion-weighted (DW) and gradient echo (GE) magnetic resonance images were acquired before and after occlusion of the middle cerebral artery (MCA) in the rat. Upon occlusion, an increase in DW imaging signal intensity was observed in a core area within the MCA territory, most likely reflecting cytotoxic edema. The signal from GE images, which is sensitive to changes in the absolute amount of deoxyhemoglobin, decreased following ischemia within a region that extended beyond the core area observed with DW imaging. This hypointensity is attributed to increases in blood volume and/or oxygen extraction fraction, which result from a decrease in perfusion pressure in the collaterally perfused area. The evolution of the GE imaging signal intensity from different regions was studied for 3.5 h following the occlusion. In the core area, the GE imaging signal returned towards baseline values after ∼1–2 h, while it remained stable in the surrounding area. This feature may reflect a decrease in hematocrit due to microcirculatory defect and/or a decrease in the oxygen extraction fraction due to ongoing infarction of the tissue and may indicate that tissue recovery is severely compromised. The combined use of DW and GE imaging offers great promise for the noninvasive identification of specific pathological events with high spatial resolution.
Ion Channel Involvement in Anoxic Depolarization Induced by Cardiac Arrest in Rat Brain
Authors: Xie Yaxia , Zacharias Elke , Hoff Patricia , Tegtmeier Frank
Published: April 2011

Anoxic depolarization (AD) and failure of ion homeostasis play an important role in ischemia-induced neuronal injury. In the present study, different drugs with known ion-channel-modulating properties were examined for their ability to interfere with cardiac-arrest-elicited AD and with the changes in the extracellular ion activity in rat brain. Our results indicate that only drugs primarily blocking membrane Na+ permeability (NBQX, R56865, and flunarizine) delayed the occurrence of AD, while compounds affecting cellular Ca2+ load (MK-801 and nimodipine) did not influence the latency time. The ischemia-induced [Na+]e reduction was attenuated by R56865. Blockade of the ATP-sensitive K+ channels with glibenclamide reduced the [K+]e increase upon ischemia, indicating an involvement of the KATP channels in ischemia-induced K+ efflux. The KATP channel opener cromakalim did not affect the AD or the [K+]e concentration. The ischemia-induced rapid decline of extracellular calcium was attenuated by receptor-operated Ca2+ channel blockers MK-801 and NBQX, but not by the voltage-operated Ca2+ channel blocker nimodipine, R56865, and flunarizine.
A Selective N-Type Calcium Channel Antagonist Reduces Extracellular Glutamate Release and Infarct Volume in Focal Cerebral Ischemia
Authors: Takizawa Shunya , Matsushima Kazushi , Fujita Hitoshi , Nanri Kazunori , Ogawa Saori , Shinohara Yukito
Published: April 2011

Although a number of studies have demonstrated the neuroprotective effects of antagonists of postsynaptic N-methyl-d-aspartate (NMDA) and non-NMDA receptors in cerebral ischemia, little is known about the treatment of cerebral infarction through presynaptic blocking of extracellular glutamate release. We evaluated the effects of a presynaptic selective N-type calcium channel antagonist (SNX-111, given intravenously by continuous infusion at 5 mg/kg/h from 20 min prior to occlusion until 2 h postocclusion) on blood flow, extracellular glutamate, and infarct volume in rats with permanent occlusions of the right middle cerebral and right common carotid arteries plus 1-h transient occlusion of the left common carotid artery. There was no significant difference in CBF in the occluded cortex during the experiment between the treated and vehicle groups. SNX-111 significantly reduced total amount of extracellular glutamate during the experiment and the peak value of the glutamate after occlusion from 44.2 ± 15.8 μ M (mean ± SD) to 21.4 ± 11.4 μ M (p < 0.01). Infusion of SNX-111 also significantly reduced the cortical volume of infarction from 47.2 ± 5.8 to 19.9 ± 7.3% (p < 0.0001). These results suggest that SNX-111 has a protective effect against focal ischemia through the inhibition of glutamate release from presynaptic sites, although SNX-111 may also affect the release of other neurotransmitters.
Regional Congruence and Divergence of Glucose Transporters (GLUT1) and Capillaries in Rat Brains
Authors: Rahner-Welsch Sylvia , Vogel Johannes , Kuschinsky Wolfgang
Published: April 2011

The association of glucose transporters (GLUT1) and brain capillaries was tested in different brain structures of rats by a direct comparison of the topologies of capillaries and GLUT1 in identical brain sections. Antibody staining of capillaries (fibronectin) and GLUT1 were made visible by fluorescence microscopy. The results showed differences between brain structures containing a tight and a leaky blood–brain barrier. All capillaries of brain structures with a tight blood–brain barrier showed congruent staining of GLUT1 and capillary morphology. The circumventricular organs that are known to have leaky barrier capillaries were stained by fibronectin antibodies but not by GLUT1 antibodies. Ependymal cells showed moderate staining by GLUT1 antibodies both in areas with tight and leaky barriers. The subcommissural organ appeared to be unique showing neither capillary nor GLUT1 stain. It is concluded that glucose transporters (GLUT1) exist in all brain capillaries of blood–brain barrier structures, whereas they are absent in leaky barrier structures. Moderate amounts of glucose transporter (GLUT1) can also be detected in ependymal cells.
Change in Cerebral Blood Flow Velocity with Onset of EEG Silence during Inhalation Anesthesia in Humans: Evidence of Flow-Metabolism Coupling?
Authors: Lam Arthur M. , Matta Basil F. , Mayberg Teresa S. , Strebel Stephan
Published: April 2011

In eight subjects anesthetized with moderate to high doses of inhalation anesthetics (isoflurane or desflurane) during normocapnia, the onset of electrical silence in EEG was associated with a sudden reduction of blood flow velocity monitored from the middle cerebral artery. The magnitude of this reduction was 38 ± 11% (mean ± SD; range 24–44%). The change in EEG always preceded the change in flow velocity by 5–7 s. These observations suggest that some flow–metabolism coupling mechanism is preserved during inhalation anesthesia in humans.