bluuebunny/crossref_metadata_2025 huggingface dataset:
Regional Difference in the Response Mediated by β1-Adrenoceptor Subtype in Bovine Cerebral Arteries
Authors: Ayajiki Kazuhide , Toda Noboru
Published: April 2011

Helical strips of bovine rostral cerebral arteries (anterior cerebral, middle cerebral, and internal carotid artery) responded to norepinephrine with contractions, whereas the caudal cerebral arteries (posterior communicating, posterior cerebral, and basilar artery) relaxed in response to the amine. After blockade of α-adrenoceptors, norepinephrine-induced rostral artery contractions were reversed to relaxations, which were smaller than those in the caudal arteries. Isoproterenol, dobutamine, and terbutaline produced greater relaxations in caudal than in rostral arteries, but forskolin relaxed these arteries to a similar magnitude. The isoproterenol-induced relaxation was not affected by removal of the endothelium. Maximal relaxations induced by terbutaline in caudal arteries were much inferior to those by isoproterenol, norepinephrine, and dobutamine. Relaxations caused by isoproterenol, norepinephrine, and terbutaline in the caudal arteries were attenuated by metoprolol, but not influenced by butoxamine. Relaxations mediated possibly by β1-adrenoceptor subtype are greater in bovine caudal cerebral arteries than in the rostral arteries. The heterogeneity does not appear to be associated with the different ability of cyclic AMP to relax arterial smooth muscle but with the difference of β-adrenoceptor populations and/or processes from the receptors to adenylate cyclase.
Ultrastructural Localization of Calcium in Ischemic Hippocampal Slices: The Influence of Adenosine and Theophylline
Authors: Dux Ernö , Schubert Peter , Kreutzberg Georg W.
Published: April 2011

Calcium was localized ultrastructurally with the use of the modified oxalate-pyroantimonate reaction in the CA1 region of rat hippocampal slices. Ten-minute ischemia (incubation with anoxic and glucose-free medium) followed by 30 min reoxygenation resulted in mitochondrial calcium sequestration and ultrastructural damage. The addition of the adenosine receptor antagonist, theophylline, worsened the ischemia-induced morphological changes and particularly exaggerated the Ca2+ loading in the postsynaptic dendrites. In contrast, adenosine protected against ischemia-induced changes. The results suggest that adenosine exerts its neuroprotective action largely by maintaining intracellular calcium-homeostasis.
Focal Cerebral Ischemia in Rats: Effects of Induced Hypertension, during Reperfusion, on CBF
Authors: Cole Daniel J. , Matsumura Jerry S. , Drummond John C. , Schell Randall M.
Published: April 2011

The effect of phenylephrine-induced hypertension on CBF was investigated after 120 min of middle cerebral artery occlusion in rats. Blood pressure was manipulated by one of the following schedules during a 90-min period of reperfusion: 90/NORM, 90 min of normotensive reperfusion; 90/HTN, 90 min of hypertensive reperfusion (MABP increased by 30 mm Hg); or 15/HTN, the 90-min period of reperfusion was divided into 30 min of normotension, followed by 15 min of hypertension and 45 min of normotension. At the end of reperfusion, 100 μCi kg−1 of [14C]iodoantipyrine was given and an autoradiographic analysis of CBF performed. In the coronal brain section at the center of middle cerebral artery distribution, the area (percentage of hemisphere, mean ± SD) with a CBF of 0–20 or 21–40 ml 100 g−1 min−1 was less (p < 0.05) in the 15/HTN group (1 ± 2 and 5 ± 3%, respectively) versus the 90/HTN group (12 ± 4 and 10 ± 4%), which was in turn less than in the 90/NORM group (18 ± 5 and 22 ± 6%). These data are consistent with the hypothesis that during reperfusion a short interval of hypertension effectively augments CBF via an abrupt opening of collapsed vessels and that a more sustained interval of hypertension conveys no added benefit.
Imaging Muscarinic Cholinergic Receptors in Human Brain in vivo with SPECT, [123I]4-Iododexetimide, and [123I]4-Iodolevetimide
Authors: Müller-Gärtner Hans W. , Wilson Alan A. , Dannals Robert F. , Wagner Henry N. , Frost J. James
Published: April 2011

A method to image muscarinic acetylcholine receptors (muscarinic receptors) noninvasively in human brain in vivo was developed using [123I]4-iododexetimide ([123I]IDex), [123I]4-iodolevetimide ([123I]ILev), and single photon emission computed tomography (SPECT). [123I]IDex is a high-affinity muscarinic receptor antagonist. [123I]ILev is its pharmacologically inactive enantiomer and measures nonspecific binding of [123I]IDex in vitro. Regional brain activity after tracer injection was measured in four young normal volunteers for 24 h. Regional [123I]IDex and [123I]ILev activities were correlated early after injection, but not after 1.5 h. [123I]IDex activity increased over 7–12 h in neocortex, neostriatum, and thalamus, but decreased immediately after the injection peak in cerebellum. [123I]IDex activity was highest in neostriatum, followed in rank order by neocortex, thalamus, and cerebellum. [123I]IDex activity correlated with muscarinic receptor concentrations in matching brain regions. In contrast, [123I]ILev activity decreased immediately after the injection peak in all brain regions and did not correspond to muscarinic receptor concentrations. [123I]IDex activity in neocortex and neostriatum during equilibrium was six to seven times higher than [123I]ILev activity. The data demonstrate that [123I]IDex binds specifically to muscarinic receptors in vivo, whereas [123I]ILev represents the nonspecific part of [123I]IDex binding. Subtraction of [123I]ILev from [123I]IDex images on a pixel-by-pixel basis therefore reflects specific [123I]IDex binding to muscarinic receptors. Owing to its high specific binding, [123I]IDex has the potential to measure small changes in muscarinic receptor characteristics in vivo with SPECT. The use of stereoisomerism directly to measure nonspecific binding of [123I]IDex in vivo may reduce complexity in modeling approaches to muscarinic acetylcholine receptors in human brain.
Effect of Photic Stimulation on Human Visual Cortex Lactate and Phosphates Using 1H and 31P Magnetic Resonance Spectroscopy
Authors: Sappey-Marinier D. , Calabrese G. , Fein G. , Hugg J. W. , Biggins C. , Weiner M. W.
Published: April 2011

Previous animal and human studies showed that photic stimulation (PS) increased cerebral blood flow and glucose uptake much more than oxygen consumption, suggesting selective activation of anaerobic glycolysis. In the present studies, image-guided 1H and 31P magnetic resonance spectroscopy (MRS) was used to monitor the changes in lactate and high-energy phosphate concentrations produced by PS of visual cortex in six normal volunteers. PS initially produced a significant rise (to 250% of control, p < 0.01) in visual cortex lactate during the first 6.4 min of PS, followed by a significant decline ( p = 0.01) as PS continued. The PCr/Pi ratios decreased significantly from control values during the first 12.8 min of PS ( p < 0.05), and the pH was slightly increased. The positive P100 deflection of the visual evoked potential recorded between 100 and 172 ms after the strobe was significantly decreased from control at 12.8 min of PS ( p < 0.05). The finding that PS caused decreased PCr/Pi is consistent with the view that increased brain activity stimulated ATPase, causing a rise in ADP that shifted the creatine kinase reaction in the direction of ATP synthesis. The rise in lactate together with an increase in pH suggest that intracellular alkalosis, caused by the shift of creatine kinase, selectively stimulated glycolysis.
Regional Cerebral l-[14C-Methyl]Methionine Incorporation into Proteins: Evidence for Methionine Recycling in the Rat Brain
Authors: Planas Anna M. , Prenant Christian , Mazoyer Bernard M. , Comar Dominique , Di Giamberardino Luigi
Published: April 2011

The specific activity (SA) of free methionine was measured in plasma and in different regions of the rat brain at 15, 30, or 60 min after intravenous infusion of l-[14C- methyl]methionine. Within these time periods, an apparent steady state of labeled free methionine in plasma and in brain was reached. However, the brain-to-plasma free methionine SA ratio was found to be ∼0.5, showing that an isotopic equilibrium between brain and plasma was not attained. This suggests the presence of an endogenous source of brain free methionine (likely originating from protein breakdown), in addition to the plasma source. The contribution of this endogenous source to the content of free methionine varies significantly among the different brain regions. Our results indicate that the regional rates of protein synthesis measured with l-[11C- methyl]methionine using positron emission tomography would be underestimated, since the local fraction of brain methionine derived from protein degradation would not be considered.
The Effect of Hypothermia on Transient Middle Cerebral Artery Occlusion in the Rat
Authors: Chen Hua , Chopp Michael , Zhang Zheng G. , Garcia Julio H.
Published: April 2011

We investigated the effect of moderate whole body hypothermia (30°C) on transient middle cerebral artery occlusion (MCAO) in the rat. Male Wistar rats were subjected to 2 h of ischemia by inserting a suture into the lumen of the internal carotid artery and occluding the origin of the MCA. Experimental groups were (a) MCAO induced at 37°C body temperature ( n = 15); (b) 30°C body temperature induced prior to ischemia and maintained for 2 h of MCAO and 1 h of reperfusion ( n = 12); and (c) MCAO with regional brain and body temperatures measured in normothermic ( n = 3) and hypothermic MCAO rats ( n = 2). Histopathological evaluation was performed 96 h after reperfusion. All normothermic MCAO animals exhibited ischemic infarct involving the ipsilateral cortex and basal ganglia with infiltration of neutrophils, macrophages, and microvascular proliferation. Hypothermic MCAO animals exhibited minor ischemic damage ranging from selective neuronal injury to small focal areas of infarct with minimal inflammatory response. Our data demonstrate that transient ischemia induced by using the intra-arterial suture method to occlude the MCA results in a reproducible brain lesion and that moderate hypothermia has a profound protective effect on the brain injury after transient MCAO.
Effect of Ischemia and Reperfusion on λ of the Lumped Constant of the [14C]Deoxyglucose Technique
Authors: Greenberg Joel H. , Hamar Janos , Welsh Frank A. , Harris Valerie , Reivich Martin
Published: April 2011

We measured the parameter λ, which is the ratio of the distribution spaces of 2-deoxy-d-glucose (DG) and glucose in the brain, in a model of focal cerebral ischemia in the cat. λ is the parameter in the lumped constant of the [14C]DG technique most susceptible to changes in ischemia. Cats were subjected to occlusion of the middle cerebral artery for a period of 2 h. During the last 60 min of occlusion, [14C]DG was infused in a programmed fashion so as to obtain a stable arterial blood [14C]DG concentration. The brain was funnel-frozen to preserve tissue metabolites and the frozen brain was sampled regionally (4 to 7-mg samples) for local concentrations of glucose, ATP, phosphocreatine (PCr), and lactate. In a separate series of cats, the infusion of [14C]DG was started after 2 h of occlusion and 3 h of recirculation. In both series, λ declined slightly for increased levels of tissue glucose and increased appreciably as tissue glucose decreased. A similar relationship was observed between λ and ATP and PCr, although the correlation was not as clear. Since λ, and hence the lumped constant, increases in ischemia as well as in postischemic tissue, it is important to measure tissue glucose concentration if quantitative values of local cerebral glucose metabolism are desired in this condition.
Changes in Neuropeptide Y after Experimental Traumatic Brain Injury in the Rat
Authors: McIntosh Tracy K. , Ferriero Donna
Published: April 2011

We utilized a model of fluid percussion (FP) brain injury in the rat to examine the hypothesis that alterations in brain neuropeptide Y (NPY) concentrations occur following brain injury. Male rats (n = 44) were subjected to FP traumatic brain injury. One group of animals (n = 38) was killed at 1 min, 15 min, 1 h, or 24 h after brain injury, and regional brain homogenates were analyzed for NPY concentrations using radioimmunoassay. A second group of animals (n = 6) was killed for NPY immunocytochemistry. Concentrations of NPY in the injured left parietal cortex were significantly elevated at 15 min post injury (p < 0.05). No changes were observed in other brain regions. NPY-immunoreactive fibers were seen at 15 min post injury predominantly in the injured cortex and adjacent hippocampus. These temporal changes in NPY immunoreactivity, together with previous observations concerning posttraumatic changes in regional CBF in these same areas, suggest that an increase in region NPY concentrations after brain injury may be involved in part in the pathogenesis of posttraumatic hypoperfusion.
Recovery of Mitochondrial and Plasma Membrane Function following Hypoglycemic Coma: Coupling of ATP Synthesis, K+ Transport, and Changes in Extra- and Intracellular pH
Authors: Katsura Ken-Ichiro , Folbergrová Jaroslava , Bengtsson Finn , Kristián Tibor , Gidö Gunilla , Siesjö Bo K.
Published: April 2011

The primary objective of the present study was to evaluate the recovery of plasma and mitochondrial membrane functions after 30 min of hypoglycemic coma and to establish whether a lingering accumulation of free fatty acids (FFAs) delays the recovery. A secondary objective was to study whether production of metabolic acids following glucose infusion leads to a fall in intracellular pH (pHi). Phosphocreatine, creatine, ATP, ADP, and AMP, as well as glycogen, glucose, lactate, pyruvate, and FFAs of rat brain cortex and caudoputamen were measured, and “free” ADP was calculated from the creatine kinase equilibrium. Extracellular pH (pHe) and K+ concentration (K+e) were measured with ion-sensitive microelectrodes, and pHi was derived by the CO2 method. Glucose injection was followed by resumption of oxidative phosphorylation within ∼2 min and by an equally rapid restoration of normal K+e levels. These functions recovered although tissue FFAs remained elevated for at least 7–8 min. Tissue lactate content increased only moderately and production of metabolic acids did not lead to intracellular acidosis. After 15 min of recovery, pHi was moderately increased, although pHe fell toward 7.0. It is speculated that the dissociation between intra- and extracellular pH is compatible with an up-regulation of an Na+/H+ antiporter, e.g., by phosphorylation.
An Electron Microscopic Immunogold Analysis of Developmental Up-Regulation of the Blood—Brain Barrier GLUT1 Glucose Transporter
Authors: Cornford Eain M. , Hyman Shigeyo , Pardridge William M.
Published: April 2011

Electron microscopy was used to quantitate blood–brain barrier (BBB) glucose transporters in newborn, 14-day-old suckling, 28-day-old weanling, and adult rabbits. A rabbit polyclonal antiserum to a synthetic peptide encoding the 13 C-terminal amino acids of the human erythrocyte glucose transporter (GLUT1) was labeled with 10-nm gold particle–secondary antibody conjugates and localized immunoreactive GLUT1 molecules in rabbit brain capillary endothelia. Three distinct populations of brain capillary profiles were identified in newborn rabbits: prepatent capillary buds, partially patent capillaries with highly amplified luminal membranes, and patent capillaries. Immunogold analyses indicated that the GLUT1 transporter abundance positively correlated with capillary developmental status. The mean number of gold particles per capillary profile increased at each developmental age examined, suggesting that developmental up-regulation of the BBB glucose transporter occurred in rabbits. GLUT1 immunoreactivity was three- to fourfold greater on the abluminal than luminal capillary membranes among all ages examined. Changes in the proportions of GLUT1 transporter were also seen, and possible reasons for the postnatal decrease in the percentage of cytoplasmic GLUT1 transporter are discussed. The numbers of cytoplasmic and membrane-associated immunogold particles increased with age. We conclude that regulatory modulations of BB glucose transport may be characterized by increases in BBB glucose transporter density with age and state of development. In addition, modulation of glucose transporter activity may be reflected by minor postnatal shifts of GLUT1 from cytoplasmic to membrane compartments, which can be demonstrated with quantitative immunogold electron microscopy.
Tetrahydroaminoacridine and Physostigmine Increase Cerebral Glucose Utilization in Specific Cortical and Subcortical Regions in the Rat
Authors: Bassant M. H. , Jazat F. , Lamour Y.
Published: April 2011

The effects of the anticholinesterases tetrahydroaminoacridine (THA) and physostigmine on local cerebral glucose utilization (LCGU) were studied in the conscious rat, using the autoradiographic [14C]deoxyglucose technique. THA (5 mg/kg i.p.) increased LCGU significantly in 8 of the 43 regions studied. A higher dose of THA (10 mg/kg) produced a metabolic activation in 19 of the 43 regions. LCGU increased in cortical areas (including parietal and temporal cortices), the septohippocampal system, the thalamus, the lateral habenula, the basolateral amygdala, the superior colliculus, and the substantia nigra. Scopolamine (4 mg/kg i.p.) reversed the THA-induced LCGU increase. Physostigmine (0.2 and 0.5 mg/ kg) increased LCGU in 15 and 22 regions, respectively. The average magnitude of the change induced by 0.5 mg/kg of physostigmine was similar to that observed after THA at 10 mg/kg, but the topography of the effects was somewhat different. Physostigmine increased LCGU in the preoptic magnocellular area, the brainstem, and the cerebellum but not in the parietal cortex. The effects in the septohippocampal system were smaller than those induced by THA. The regional topography of the LCGU increase overlapped the distribution of the M2 muscarinic receptors and that of acetylcholinesterase activity. These data suggest that the major effects of THA and physostigmine on LCGU result from their anticholinesterase action.
Dynamic High-Resolution MR Imaging of Brain Deoxygenation during Transient Anoxia in the Anesthetized Rat
Authors: Prielmeier Franz , Merboldt Klaus-Dietmar , Hänicke Wolfgang , Frahm Jens
Published: April 2011

Transient alterations in brain oxygenation during 60-s periods of anoxia were visualized at high spatial resolution (voxel size ≤ 0.15 μl) with the use of serial long echo time FLASH (fast low-angle shot) magnetic resonance images (measuring time ≥ 6 s) of halothaneanesthetized rats in vivo. Difference images from normoxia and anoxia exploit the signal decrease associated with increased levels of paramagnetic deoxyhemoglobin in the arterial and venous blood pool. Insights into the spatial heterogeneity of oxygen deprivation are complemented by physiologic information from the time course of pertinent signal changes in different regions of the brain.
Localized Dynamic Changes in Cortical Blood Flow with Whisker Stimulation Corresponds to Matched Vascular and Neuronal Architecture of Rat Barrels
Authors: Cox Stephanie B. , Woolsey Thomas A. , Rovainen Carl M.
Published: April 2011

The hypothesis that functional groups of neurons in whisker barrels are linked to a modular organization of cortical vessels was tested. Endovascular casts demonstrated cortical capillary networks resembling the whisker barrel pattern that were fed from the middle cerebral artery. In histological sections, dense capillaries apparently were confined to single barrels and were supplied by one or a few penetrating arterioles. The barrel field in cortical layer IV was localized in relation to surface arteriovenous patterns. Living vessels were imaged through a closed cranial window under anesthesia with a fluorescence microscope and SIT or ICCD cameras. After intracarotid injections of fluorescein isothiocyanate–dextrans, saline, or 3 μm latex beads, changes in arteriolar diameter, arteriovenous transit times (AVTTs), and bead velocities were measured. When row C whiskers were stroked at 4–5 Hz for 1 min, blood flow increased in arterioles that supplied contralateral row C barrels as demonstrated by postmortem histology. AVTTs slowed significantly in vessels supplying adjacent cortex. We hypothesize that cerebral vascular units supply individual whisker barrels and are functionally linked to them for precise focal regulation of cerebral blood flow.
Treatment with an AMPA Antagonist 12 Hours following Severe Normothermic Forebrain Ischemia Prevents CA1 Neuronal Injury
Authors: Li Hui , Buchan Alastair M.
Published: April 2011

The neuroprotective effects of 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo( f)quinoxaline (NBQX), GYKI 52466, and MK-801 were tested following severe forebrain ischemia. Wistar rats were subjected to 10 min of normothermic ischemia and reperfused for 7 days. Necrotic hippocampal CA1 neurons were counted and expressed as a percentage (mean ± SD). In Experiment 1, saline-treated rats sustained 81 ± 20% damage to dorsal CA1. Rats given NBQX 30 mg/kg i.p. x 3 lost 21 ± 27% (p < 0.01). Neither MK-801 1 mg i.p. x 3 alone, nor in combination with the cytoprotective dose of NBQX protected CA1, with 83 ± 18 and 54 ± 34% damage, respectively (NS). Giving NBQX 90 mg/kg i.v. did not protect cells (94 ± 5%) and resulted in nephrotoxicity. In Experiment 2, rats were given saline or three doses of NBQX 30 mg/kg i.p. immediately at reperfusion (RP) or after a 6-, 12-, or 24-h delay. Saline-treated rats suffered 79 ± 16% injury. NBQX given immediately resulted in 17 ± 17% injury, and even if treatment was delayed by either 6 or 12 h, there was marked protection with only 27 ± 32 and 25 ± 17% injury, respectively (all p < 0.01). Delaying the initiation of treatment to 24 h was not successful, resulting in 50 ± 28% injury (NS). In Experiment 3, saline-treated rats lost 81 ± 19% of CA1 cells, while those given GYKI 52466 10 mg/kg i.p. x 5 starting immediately following RP lost 80 ± 14%. Blocking α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors with NBQX postischemia is highly efficacious, indicating that delayed degeneration of CA1 cells is AMPA rather than N-methyl-d-aspartate (NMDA) receptor-linked and is reversible for CA1 cells for at least 12 h.
Selective Reductions in the Activity of the Pyruvate Dehydrogenase Complex in Mitochondria Isolated from Brain Subregions following Forebrain Ischemia in Rats
Authors: Zaidan Emad , Sims Neil R.
Published: April 2011

Previous studies showed that in rats exposed to 30 min of forebrain ischemia, there were reductions in pyruvate-supported respiration within the first 3 h of recirculation in mitochondria isolated from the dorsolateral striatum (a region in which the majority of neurons are susceptible to ischemia) but not the ischemia-resistant paramedian neocortex. The present study demonstrates that the changes in mitochondrial respiration apparently result from a loss of activity of the pyruvate dehydrogenase complex (PDHC). In mitochondria from the dorsolateral striatum, incubated in the presence of pyruvate and ADP (state 3 conditions) and treated to preserve the phosphorylation state of PDHC, there was no significant change from preischemic activity after 30 min of ischemia or 1 h of recirculation. However, a significant reduction (to 71% of control value) was observed at 3 h of recirculation, and the activity decreased further at 6 and 24 h (to 64 and 43% of control values, respectively). Total PDHC activity in the isolated mitochondria was similarly reduced at 3 h (68% of control values) and 6 h (73% of control values), indicating that the alteration was due to loss or inactivation of the PDHC rather than changes in phosphorylation of the complex. No significant changes were observed in the activity of two other mitochondrial markers, rotenone-sensitive NADH-cytochrome c oxidoreductase and α-ketoglutarate dehydrogenase. None of the activities of these three enzymes in mitochondria from the paramedian neocortex was significantly affected by ischemia or recirculation. These results (together with previous observations) indicate an early and specific change affecting the PDHC in cells of the dorsolateral striatum. This change occurs sufficiently early that it could contribute to the degenerative process in affected cells. At a minimum, the change in PDHC provides an early marker for degeneration in the dorsolateral striatum.
Local NADPH—Diaphorase Neurons Innervate Pial Arteries and Lie Close or Project to Intracerebral Blood Vessels: A Possible Role for Nitric Oxide in the Regulation of Cerebral Blood Flow
Authors: Estrada Carmen , Mengual Elisa , González Carmen
Published: April 2011

Electrical stimulation of perivascular nerves induced a relaxation of endothelium-denuded cat pial arteries that was significantly reduced by nitric oxide (NO) synthase inhibition, indicating that NO was involved in the neurogenic relaxation of these vessels. Histochemical staining of the pial arteries for NADPH-diaphorase (NADPH-d), used as a marker for NO synthase, showed positive nerve fibers in the adventitial layer. Interestingly, in some restricted areas stained neuronal cell bodies were also observed. These neurons were scattered or distributed in small groups in a ganglion-like manner, and they sent fibers to the vessel wall. No NADPH-d-positive nerve fibers or cell bodies were detected in forelimb, pulmonary, or coronary arteries. Within the brain parenchyma, blood vessels also showed positive fibers around their walls. These fibers were organized in a branching pattern and presented varicosities. NADPH-d-positive neurons were found in the proximity of the intracerebral vascular profiles, sending processes to the vessels and/or being directly apposed to their wall. The neurovascular contacts were preferentially located close to the interface between the cerebral cortex and white matter. The anatomical relationship between NADPH-d-positive neurons and fibers and the cerebral blood vessels, together with the participation of NO in the neurogenic relaxation of pial arteries, suggests that NO is involved in the regulation of cerebral blood flow.
Effects of Axotomy on Protein Synthesis in the Rat Hypoglossal Nucleus: Examination of the Influence of Local Recycling of Leucine Derived from Protein Degradation into the Precursor Pool
Authors: Sun Y. , Deibler G. E. , Smith C. Beebe
Published: April 2011

The quantitative autoradiographic l-[1-14C] leucine method for the determination of regional rates of cerebral protein synthesis (lCPSleu) requires knowledge of the degree of recycling of leucine derived from protein degradation into the precursor pool for protein synthesis, which can be evaluated by measuring λi; the steady-state ratio of the leucine-specific activity in the precursor amino acid pool (tRNA-bound leucine) to that of the arterial plasma. To define the changes in lCPSleu during regeneration of the hypoglossal nerve, we examined the effects of axotomy on the value of λi. Because the concentration of tRNA-bound leucine in the hypoglossal nucleus is too low to measure, we measured the equivalent ratio for the total acid-soluble pool (ψi) and applied the linear relationship between λ and ψ found in the whole brain to calculate a value of λi in the ipsilateral and contralateral hypoglossal nuclei of 22 adult female rats 2, 18, 35, and 60 days after unilateral hypoglossal axotomy. Statistically significant but quantitatively inconsequential effects of axotomy on values of ψi and λi were found. Therefore, the mean value for λi (0.64) of the left and right hypoglossal nuclei in all 22 axotomized rats was used to calculate lCPSleu. In a separate group of 15 unilaterally axotomized rats, lCPSleu was determined by the autoradiographic technique; lCPSleu was increased on the axotomized side by 23% on day 2, 30% on day 18, and 13% on day 35. By postaxotomy day 60, lCPSleu had returned to normal.
Fastigial Stimulation Increases Ischemic Blood Flow and Reduces Brain Damage after Focal Ischemia
Authors: Zhang Fangyi , Iadecola Costantino
Published: April 2011

Electrical stimulation of the cerebellar fastigial nucleus (FN) increases CBF and reduces brain damage after focal ischemia. We studied whether FN stimulation “protects” the brain from ischemic damage by increasing blood flow to the ischemic territory. Sprague–Dawley rats were anesthetized (halothane 1–3%) and artificially ventilated through a tracheal cannula inserted transorally. CBF was monitored by a laser-Doppler probe placed over the convexity at a site corresponding to the area spared from infarction by FN stimulation. Arterial pressure (AP), blood gases, and body temperature were controlled, and the electroencephalogram (EEG) was monitored. The stem of the middle cerebral artery (MCA) was occluded. After occlusion, the FN was stimulated for 60 min (100 μA; 50 Hz; 1 s on–1 s off) while AP was maintained at 97 ± 11 mm Hg (mean ± SD) by controlled hemorrhage. Rats were then allowed to recover, and infarct volume was determined 24 h later in thioninstained sections. In unstimulated rats ( n = 7), proximal MCA occlusion reduced CBF and the amplitude of the EEG. One day later, these rats had infarcts involving neocortex and striatum. FN stimulation after MCA occlusion ( n = 12) enhanced CBF and EEG recovery [61 ± 34 and 73 ± 43%, respectively at 60 min; p < 0.05 vs. unstimulated group; analysis of variance (ANOVA)] and reduced the volume of the cortical infarct by 48% (p < 0.05). In contrast, hypercapnia (Pco2 = 64 ± 4; n = 7) did not affect CBF and EEG recovery or infarct volume (p > 0.05). Thus, FN stimulation, unlike hypercapnia, increases CBF to the ischemic cortex, improves recovery of electrical activity, and reduces tissue damage after MCA occlusion. These findings support the hypothesis that FN stimulation reduces ischemic damage by enhancing collateral flow to the ischemic territory.
Immunolocalization of Heat Shock Protein after Fluid Percussive Brain Injury and Relationship to Breakdown of the Blood-Brain Barrier
Authors: Tanno Hirokazu , Nockels Russ P. , Pitts Lawrence H. , Noble Linda J.
Published: April 2011

We have previously developed a model of mild, lateral fluid percussive head injury in the rat and demonstrated that although this injury produced minimal hemorrhage, breakdown of the blood–brain barrier was a prominent feature. The relationship between posttraumatic blood–brain barrier disruption and cellular injury is unclear. In the present study we examined the distribution and time course of expression of the stress protein HSP72 after brain injury and compared these findings with the known pattern of breakdown of the blood–brain barrier after a similar injury. Rats were subjected to a lateral fluid percussive brain injury (4.8–5.2 atm, 20 ms) and killed at 1, 3, and 6 h and 1,3, and 7 days after injury. HSP72-like immunoreactivity was evaluated in sections of brain at the light-microscopic level. The earliest expression of HSP72 occurred at 3 h postinjury and was restricted to neurons and glia in the cortex surrounding a necrotic area at the impact site. By 6 h, light immunostaining was also noted in the pia-arachnoid adjacent to the impact site and in certain blood vessels that coursed through the area of necrosis. Maximal immunostaining was observed by 24 h postinjury, and was primarily associated with the cortex immediately adjacent to the region of necrosis at the impact site. This region consisted of darkly immunostained neurons, glia, and blood vessels. Immunostaining within the region of necrosis was restricted to blood vessels. HSP72-like immunoreactivity was also noted in a limited number of neurons and glia in other brain regions, including the parasagittal cortex, deep cortical layer VI, and CA3 in the posterior hippocampus. Immunoreactive cells in these areas were not apparent until 24 h postinjury. By 7 days postinjury, HSP72-like immunoreactivity was minimal or absent in these injured brains and notable cell loss was apparent only in the impact site. This study demonstrates an early and pronounced expression of HSP72 at the impact site and a more delayed and less prominent expression of this protein in other regions of the brain. These findings parallel the temporal and regional pattern of breakdown of the blood–brain barrier after a similar head injury.
Hydrogen Peroxide Production by Monoamine Oxidase during Ischemia-Reperfusion in the Rat Brain
Authors: Simonson Steven G. , Zhang Jing , Canada Andrew T. , Su Ying-Fu , Benveniste Helene , Piantadosi Claude A.
Published: April 2011

Monoamine oxidase (MAO) as a source of hydrogen peroxide (H2O2) was evaluated during ischemiareperfusion in vivo in the rat brain. H2O2 production was assessed with and without inhibition of MAO during and after 15 min of ischemia. Metabolism of H2O2 by catalase during ischemia and reperfusion was measured in forebrain homogenates using aminotriazole (ATZ), an irreversible H2O2-dependent inhibitor of catalase. Catecholamine and glutathione concentrations in forebrain were measured with and without MAO inhibitors. During ischemia, forebrain blood flow was reduced to 8% of baseline and H2O2 production decreased as measured at the microperoxisome. During reperfusion, a rapid increase in H2O2 generation occurred within 5 min as measured by a threefold increase in oxidized glutathione (GSSG). The H2O2-dependent rates of ATZ inactivation of catalase between control and ischemia–reperfusion were similar, indicating that H2O2 was more available to glutathione peroxidase than to catalase in this model. MAO inhibitors eliminated the biochemical indications of increased H2O2 production and increased the catecholamine concentrations. Mortality was 67% at 48 h after ischemiareperfusion, and there was no improvement in survival after inhibition of MAO. We conclude that MAO is an important source of H2O2 generation early in brain reperfusion, but inhibition of the enzyme does not improve survival in this model despite ablating H2O2 production.
Induction of Copper-Zinc Superoxide Dismutase in Gerbil Hippocampus after Ischemia
Authors: Matsuyama Tomohiro , Michishita Hisamasa , Nakamura Hitoshi , Tsuchiyama Masato , Shimizu Souichiro , Watanabe Keiichi , Sugita Minoru
Published: April 2011

To assess the role of Cu-Zn superoxide dismutase (CuZnSOD) in regulating cellular antioxidant defenses, we studied the induction of CuZnSOD mRNA by an in situ hybridization technique and of CuZnSOD protein by an immunocytochemical method in the gerbil hippocampus following 5 min of transient global ischemia. For hybridization, we synthesized 48-mer oligonucleotide (base 465–512) complementary to rat CuZnSOD mRNA. Northern blot analysis showed hybridization to a single band of molecular weight 0.65 kb. After 5 min of ischemia, the signal became stronger at 3 and 24 h and returned to the control level 3 days later. In situ hybridization histochemistry revealed an increase in labeling throughout the hippocampus, especially in the granular layer 3 h following ischemia. The increase was prolonged only in the CA1 pyramidal layer after 24 h and was eliminated within 3 days or later. Conversely, analysis by Western blotting revealed that the insult produced few effects on the induction of CuZnSOD protein. Immunocytochemistry for CuZnSOD revealed a reduced immunostaining in the CA1 pyramidal layer at 24 h of recirculation when the persistent expression of CuZnSOD mRNA was shown in the same area. Our findings suggest that the expression of endogenous CuZnSOD is temporarily stimulated by an ischemic insult without increasing the protein level. The prolonged increase in mRNA and the decrease in the protein of CuZnSOD in the CA, neurons seem to imply an important role of the endogenous antioxidant enzyme that protects against the detrimental effects of superoxide radicals on delayed neuronal death.
Basic Fibroblast Growth Factor Protects against Hypoxia-Ischemia and NMDA Neurotoxicity in Neonatal Rats
Authors: Nozaki Kazuhiko , Finklestein Seth P. , Beal M. Flint
Published: April 2011

Basic fibroblast growth factor (bFGF) is a polypeptide that promotes neuronal survival and blocks excitatory amino acid (EAA) neurotoxicity in vitro at very low concentrations. In the present study, we examined whether systemically administered bFGF could prevent neuronal damage induced by either EAAs or hypoxia–ischemia in vivo. Neuroprotective effects were examined in a neonatal model of hypoxia–ischemia (unilateral ligation of the carotid artery followed by exposure to 8% oxygen for 1.5 h) and following intrastriatal injection of N-methyl-d-aspartate (NMDA) in 7-day-old rats. Intraperitoneal administration of a single dose of bFGF (50–300 μg/kg) 30 min before intrastriatal injection of NMDA showed a dose-dependent neuroprotective effect. Repeated doses of bFGF (100 μg/kg) both before and after intrastriatal NMDA injection produced a much greater significant protective effect than a single dose administered prior to the injection. Intraperitoneal injection of single dose of 100 μg/kg of bFGF 30 min before hypoxia–ischemia reduced neuronal damage by 38% (p = 0.14), while administration of bFGF at a dose of 100 μg/kg i.p. three times, 30 min before and 0 and 30 min after hypoxia–ischemia, significantly reduced neuronal damage by 64% (p = 0.004). Systemic administration of bFGF did not change body temperature for up to 3 h. These results show that systemic administration of bFGF can exert neuroprotective effects against both NMDA-induced excitotoxicity and hypoxia–ischemia in vivo.
Role of Protein Kinase C in the Pathogenesis of Cerebral Vasospasm after Subarachnoid Hemorrhage
Authors: Sako Masaharu , Nishihara Jun , Ohta Shinsuke , Wang Jinze , Sakaki Saburo
Published: April 2011

This study investigated the role of protein kinase C (PKC) in the pathogenesis of vasospasm after experimental subarachnoid hemorrhage (SAH). PKC activation by intracisternal injection of a phorbol ester [12- O-tetradecanoylphorbol-13-acetate (TP)] induced dose-dependent, slowly developing, severe contraction of the basilar artery. A single intracisternal injection of TP (5 × 10−9 M in the CSF) induced sustained contraction lasting over 3 days, which almost paralleled the changes of membrane-bound PKC activity in the basilar arterial wall. In a two-hemorrhage SAH model, membrane-bound PKC activity in the basilar artery increased up to day 4 and returned to the control level by day 14, whereas angiographic contraction reached a maximum on day 7 and still persisted at a moderate level on day 14. Thus, there was a discrepancy between arterial PKC activity and arterial contraction. Multiple intracisternal injections of TP produced 30–40% sustained contraction of the basilar artery lasting for more than 10 days along with sustained activation of PKC to levels compatible with that observed in the SAH model. However, TP injection caused considerably milder histological changes in the basilar artery than those noted in the SAH model. We concluded that cerebral vasospasm after SAH cannot be explained solely on the basis of activation of the PKC pathway.
Effect of Cervical Sympathectomy and Hypoxia on the Heterogeneity of O2 Saturation of Small Cerebrocortical Veins
Authors: Wei Hwu Meei , Chen Wei Yu , Sinha Arabinda K. , Weiss Harvey R.
Published: April 2011

This study evaluated the hypothesis that the sympathetic nervous system was one of the factors increasing the heterogeneity of cerebrocortical venous O2 saturation and this heterogeneity would be greater during hypoxia when cervical sympathetic activity was elevated. Thirty-two male Long–Evans rats were either sham operated ( n = 16) or received bilateral cervical sympathectomy ( n = 16). One-half of the animals ( n = 8) in each treatment were challenged by hypoxia (8% O2 in N2). Cerebral blood flow was determined in five brain regions with [14C]iodoantipyrine. Oxygen saturation was measured microspectrophotometrically in small cerebrocortical arteries and veins. The degree of hypoxic hyperemia was not significantly different between sham-operated and sympathectomized rats. Cortical venous O2 saturations, indicating the balance between O2 supply and consumption, were significantly more heterogeneous in the sham-operated group under both normoxic and hypoxic conditions. The coefficient of variation (CV = 100 × SD/mean) for the normoxic sham-operated animals was 24.9% and the average venous O2 saturation was 53.8%. During hypoxia, venous O2 saturation was significantly decreased to 43.1% without a change in CV (24.5%). Sympathectomy significantly reduced this heterogeneity through a reduction in the number of low O2 saturation veins (CV = 13.2%) under normoxic conditions and the effect was similar under hypoxic conditions (CV = 15.3%). In both sham-operated and sympathectomized groups, hypoxia elicited a significantly higher cerebrocortical O2 consumption. Thus, bilateral cervical sympathectomy improved the O2 supply in selective cerebrocortical regions with high O2 extraction. However, the effect of sympathetic innervation on the heterogeneity of cerebrocortical venous O2 saturation was not potentiated by hypoxia. This may suggest that peripheral sympathetic fibers innervate a fixed number of cerebrocortical vessels and, regardless of its intensity, this innervation exerts similar effects on the cerebrocortical venous O2 saturation.
Functional Connectivity: The Principal-Component Analysis of Large (PET) Data Sets
Authors: Friston K. J. , Frith C. D. , Liddle P. F. , Frackowiak R. S. J.
Published: April 2011

The distributed brain systems associated with performance of a verbal fluency task were identified in a nondirected correlational analysis of neurophysiological data obtained with positron tomography. This analysis used a recursive principal-component analysis developed specifically for large data sets. This analysis is interpreted in terms of functional connectivity, defined as the temporal correlation of a neurophysiological index measured in different brain areas. The results suggest that the variance in neurophysiological measurements, introduced experimentally, was accounted for by two independent principal components. The first, and considerably larger, highlighted an intentional brain system seen in previous studies of verbal fluency. The second identified a distributed brain system including the anterior cingulate and Wernicke's area that reflected monotonic time effects. We propose that this system has an attentional bias.
Microwave Fixation for the Determination of Cerebral Blood Volume in Rats
Authors: Todd Michael M. , Weeks Julie B. , Warner David S.
Published: April 2011

The cerebral blood volume (CBV) is sensitive to changing hydrostatic pressures. Thus, measurement methods that rely on removing tissue from unfixed brain may lead to underestimates of the CBV due to the loss of blood from the tissue. In situ fixation of tissue before removal may offer improved accuracy. We employed a triple-label method to measure simultaneously whole brain CBF and CBV in halothane-anesthetized Sprague–Dawley rats, which were then killed either by focused microwave irradiation (≈8 kW of incident power × 770 ms) or by decapitation. CBF was measured with [3H]nicotine while the CBV was determined as the sum of the cerebral red cell volume (CRCV—measured with 99mTc-labeled red cells) and the cerebral plasma volume (CPV—measured with [14C]dextran). Animals were studied during hypocarbic (Paco2 ≈ 25 mm Hg), normocarbic, or hypercarbic (Paco2 ≈ 70 mm Hg) conditions. Added studies were performed to verify that the microwave irradiation scheme used was capable of fixing previously administered tracers in place, and also halting the entry of tracer given after irradiation. Results indicate that the method of killing had no effects on CBF measurements, as assessed either by absolute values during normocarbia or responsiveness to changing Paco2. However, all three volume measurements made using nondiffusible tracers (CRCV, CPV, and CBV) were significantly lower in animals killed by decapitation. Furthermore, CO2 responsiveness for all three variables (as assessed by the slope of the Paco2/volume) was not evident in decapitated animals. We conclude that in situ fixation offers significant advantages when examining the cerebral distribution space of nondiffusible tracers.
Characterization of the Cerebroprotective Efficacy of the Competitive NMDA Receptor Antagonist CGP40116 in a Rat Model of Focal Cerebral Ischemia: An in vivo Magnetic Resonance Imaging Study
Authors: Sauer Dirk , Allegrini Peter R. , Cosenti Alexandra , Pataki Alexander , Amacker Hugo , Fagg Graham E.
Published: April 2011

The cerebroprotective properties of the competitive NMDA antagonist d-( E)-2-amino-4-methyl-5-phosphono-3-pentenoic acid (CGP 40116) were evaluated in a rat model of focal cerebral ischemia. CGP 40116 (5–40 mg/kg i.v.) was injected immediately following permanent occlusion of the left middle cerebral artery (MCA). MK 801 (1 or 3 mg/kg i.v.), d-CPPene (20 mg/kg i.v.), and CGS 19755 (40 mg/kg i.v.) were used for comparison. Lesion volume was assessed using in vivo magnetic resonance imaging, which in initial experiments with parallel histological determinations proved to be an accurate method for the measurement of brain infarction and the determination of a cerebroprotective drug effect. CGP 40116 dose-dependently reduced the volume of cortical infarction, with an ED50 of 11 mg/kg i.v. and a maximal effect equivalent to a 62% reduction in cortical edema volume. Its cerebroprotective efficacy was thus comparable to that of MK 801. The rank order of potency for the NMDA antagonists was MK 801 > CGP 40116 ∼ d-CPPene > CGS 19755. Neuroprotection by CGP 40116 was still apparent when treatment was started 30 min after MCA occlusion. It is concluded that CGP 40116 is an effective cerebroprotectant with potential clinical utility for amelioration of focal cerebral ischemic damage.
Blockade of AMPA Receptors Reduces Brain Edema following Opening of the Blood—Brain Barrier
Authors: Westergren Irena , Johansson Barbro B.
Published: April 2011

The aim of our study was to evaluate whether blockade of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors could reduce brain edema in two experimental models of edema following opening of the blood–brain barrier (BBB). The brain specific gravity was determined 2 h after opening the BBB by a 30-s infusion of protamine sulfate (10 mg in 200 μl 0.9% NaCl) or arabinose (1.5 or 1.8 mol/L, 0.06 ml · s−1) into the right internal carotid artery. Cisternal CSF was withdrawn for albumin determination before the carotid infusion and before killing 2 h later. After infusion of protamine sulfate or arabinose, CSF albumin increased in all groups. The brain specific gravity was significantly lower in the right than in the left (control) frontal, parietal, and occipital cortex and striatum. NBQX (2,3-dihydroxy-6-nitro-7-sulfamoylbenxo( F)quinoxaline), an AMPA receptor antagonist, given intravenously 10 min after opening the BBB (5 mg/kg), significantly increased the specific gravity in the treated rats ( p < 0.01 for the difference from control rats) without reducing CSF albumin or albumin extravasation in the brain as evaluated with Evans blue. We hypothesize that intracerebral (glial?) AMPA receptors may play a role in brain edema following opening of the BBB.