bluuebunny/crossref_metadata_2025 huggingface dataset:
Cerebral Ischemia after Bilateral Carotid Artery Occlusion and Intraluminal Suture Occlusion in Mice: Evaluation of the Patency of the Posterior Communicating Artery
Authors: Kitagawa Kazuo , Matsumoto Masayasu , Yang Gongming , Mabuchi Takuma , Yagita Yoshiki , Hori Masatsugu , Yanagihara Takehiko
Published: November 2003

Cerebral ischemia models using mice have drawn increasing attention, particularly because of the availability of transgenic animals. However, the variability of intracranial vasculature at the circle of Willis in mice can influence the degree of ischemia in both the bilateral common carotid artery (CCA) occlusion and intraluminal suture occlusion models. We have developed a method to predict the extent of the anastomosis between carotid and vertebrobasilar circulation in three mouse strains (C57BL/6, CBA, and DBA/2) by measuring cortical microperfusion with laser Doppler flowmetry during a 1-minute occlusion of both CCA. When animals showed residual cortical microperfusion of less than 12% during bilateral CCA occlusion, the mice showed absence of functional anastomosis, developed ATP depletion in the frontal cortex during occlusion, and had ischemic neuronal death in the hippocampus and caudoputamen after occlusion for 15 minutes and recirculation for 7 days. Furthermore, those mice exhibited decreased local cerebral blood flow and associated ischemic neuronal death in the hippocampus, within the territory supplied by the posterior cerebral artery, with the intraluminal suture occlusion model. The current study demonstrates the need for assessment of intracranial vasculature in each animal by measuring cortical microperfusion during temporary occlusion of both CCA, no matter whether cerebral ischemia is produced by bilateral CCA occlusion or intraluminal suture occlusion in transgenic mice.
Cerebral Glucose Transport and Metabolism in Preterm Human Infants
Authors: Powers William J. , Rosenbaum Joan L. , Dence Carmen S. , Markham Joanne , Videen Tom O.
Published: November 2003

Few data regarding early developmental changes in cerebral (blood-to-brain) glucose transport (CTXglc) and CMRglc are available for humans. We measured CBF, CTXglc, and CMRglc with positron emission tomography at 4 to 7 days of life in six preterm human infants whose estimated gestational age was 25 to 34 weeks. The Michaelis-Menten constants Kt and Tmax were estimated from CTXglc and the calculated cerebral capillary plasma glucose concentration. Mean CMRglc was 8.8 μmol 100 g−1 min−1. The CMRglc did not correlate with plasma glucose concentration ( r = .315, P = .543), whereas CTXglc showed a significant correlation with plasma glucose concentration ( r = .836, P = .038). Estimation of the Michaelis-Menten constants from the best fit to the measured data produced values of Kt = 6.0 μmol mL−1 and Tmax = 32.6 μmol 100 g−1 min−1. These values for Kt in the developing human brain are similar to those that have been reported for the mature brain of adolescent and adult humans and adult nonhuman primates, indicating the affinity of the glucose transport protein for d-glucose is similar. However, Tmax is approximately one third to one half of the comparable values for mature brain, indicating a reduced number of available luminal transporters.
Changes in Protein Synthesis and Calcium Homeostasis in the Thalamus of Spontaneously Hypertensive Rats with Focal Cerebral Ischemia
Authors: Watanabe Hideaki , Kumon Yoshiaki , Ohta Shinsuke , Sakaki Saburo , Matsuda Seiji , Sakanaka Masahiro
Published: November 2003

The thalamus has been shown to undergo secondary degeneration after cerebrocortical ischemia. However, little is known about the time course of the retrograde thalamic degeneration. The present study was designed to investigate time-dependent changes in the morphology, protein synthesis and calcium metabolism of thalamic neurons in middle cerebral artery (MCA)-occluded spontaneously hypertensive stroke-prone rats that showed primary focal ischemia in the temporoparietal cortex after permanent occlusion of the left distal MCA. In the histologic study by light and electron microscopy, swelling of the nucleus and shrinkage of the perikarya were seen in some neurons of the ventroposterior (VP) thalamic nucleus on the lesioned side at 5 days after ischemia. At the same time, the incorporation of radiolabeled leucine in VP thalamic neurons began to decrease significantly with concomitant a decrease in the number of polyribosomes in the neurons. Conspicuous 45Ca accumulation was noted at 3 days after ischemia and persisted up to 1 month in the VP thalamic nucleus on the lesioned side. These findings suggest that the secondary thalamic degeneration after cortical infarction starts with disruption of calcium homeostasis in situ at the third day after MCA occlusion, followed by a decrease in polyribosomes but not by disaggregation of polyribosomes as seen in hippocampal CA1 neurons subjected to transient forebrain ischemia.
Decreased Expression and Functionality of NMDA Receptor Complexes Persist in the CA1, but Not in the Dentate Gyrus after Transient Cerebral Ischemia
Authors: Hsu Jee Ching , Zhang Yu , Takagi Norio , Gurd James W. , Wallace M. Christopher , Zhang Liang , Eubanks James H.
Published: November 2003

The authors investigated the gene expression of the NR2A and NR2B subunits of N-methyl-D-aspartate (NMDA) receptor and the functional electrophysiologic activity of NMDA receptor complexes in the vulnerable CA1 and less vulnerable dentate gyrus subfields of the rat hippocampus at different times after transient cerebral ischemia. Decreased expression for both subtypes was observed in both the CA1 subfield and dentate granule cell layer at early times after challenge; however, the decreased expression in the dentate granule cell layer was reversible because mRNA levels for both the NR2A and NR2B subtypes recovered to, or surpassed, sham-operated mRNA levels by 3 days postchallenge. No recovery of expression for either subtype was observed in the CA1 subfield. The functional activity of NMDA receptor complexes, as assessed by slow field excitatory postsynaptic potentiations (slow f-EPSP) in CA1 pyramidal neurons, was maintained at 6 hours postchallenge; however, this activity was diminished greatly by 24 hours postchallenge, and absent at 7 days postchallenge. A similar pattern was observed for the non-NMDA receptor-mediated fast f-EPSP. In dentate granule neurons, however, no significant change in NMDA receptor-mediated slow f-EPSP from sham control was observed at any time after insult. The non-NMDA receptor-generated fast f-EPSPs also were maintained at all times postinsult in the dentate gyrus. These results illustrate that the activity of NMDA receptors remains functional in dentate granule neurons, but not in the pyramidal neurons of the CA1 subfield, at early and intermediate times after transient cerebral ischemia, and suggest that there is a differential effect of ischemia on the glutamatergic transmission systems in these two hippocampal subfields.
Impairment in Biochemical Level of Arterial Dilative Capability of a Cyclic Nucleotides-Dependent Pathway by Induced Vasospasm in the Canine Basilar Artery
Authors: Todo Hirooki , Ohta Shinsuke , Wang Jinze , Ichikawa Haruhisa , Ohue Shiro , Kumon Yoshiaki , Sakaki Saburo
Published: November 2003

The authors investigated the changes and the potential of cyclic nucleotide-dependent signal transduction, which induces smooth muscle relaxation, in the basilar artery with severe vasospasm in dogs with double experimental subarachnoid hemorrhage (SAH) to explore at which biochemical level the arterial dilative capability was impaired. The amount of cyclic adenosine and guanosine monophosphates (cAMP and cGMP) decreased significantly in the basilar artery after SAH. The activities of adenylate and guanylate cyclases also were decreased significantly in the smooth muscle cells of the basilar artery 4 days after SAH. In addition to the failure of the pathways to produce cyclic nucleotides, the activities of cAMP-and cGMP-dependent protein kinases, which are representative actual enzymes that amplify the signal for vascular dilation, also significantly decreased together with the almost total loss of activation by cyclic nucleotides in the same basilar artery after SAH. It was revealed that the system for smooth muscle relaxation was impaired severely in the cerebral arteries with severe vasospasm after SAH, on the biochemical basis of significantly less vasodilative capability and in several of the steps to produce the cyclic nucleotides of intracellular signal transduction.
Induction of Heme Oxygenase-1 and Major Histocompatibility Complex Antigens in Transient Forebrain Ischemia
Authors: Matsuoka Yasuji , Kitamura Yoshihisa , Okazaki Mitsuhiro , Sakata Masahiro , Tsukahara Tetsuya , Taniguchi Takashi
Published: November 2003

Recent studies strongly suggest that oxidative stresses participate in ischemia/reperfusion-induced neurode-generation. In addition, heme oxygenase (HO) and major histocompatibility complex (MHC) antigens serve as functional molecules against oxidative stress and as self-recognition markers in the immune system, respectively. In this study, we examined the induction of HO and MHC antigens in the rat hippocampus after transient forebrain ischemia. The protein level of HO-1 was significantly enhanced after an episode of ischemia. After ischemia, HO-1 expression was observed early but transiently in the CA1 pyramidal neurons and later but continuously in glial cells. Glial cells expressing HO-1 were predominantly ameboid microglia, but not astrocytes. Ameboid microglia expressing HO-1 were predominantly localized with MHC class II antigens. These results indicate that (1) HO-1 expression in CA1 pyramidal neurons may be harmful, and (2) ischemia induces HO-1 in ameboid microglia that express MHC class II antigens, indicating a very specific microglial stress protein response.
Exacerbation of Ischemic Brain Damage by Localized Striatal Injection of Interleukin-1β in the Rat
Authors: Stroemer R. Paul , Rothwell Nancy J.
Published: November 2003

Interleukin-1β (IL-1β) has been implicated in ischemic brain damage. The site of action of IL-1β in such damage is not known, but we have demonstrated previously that injection of the interleukin-1 receptor antagonist (IL-1ra) in the striatum but not the cortex of rats inhibits damage caused by permanent middle cerebral artery occlusion. The present study investigated the site of action of IL-1β on ischemic damage by examining the effects of intracerebroventricular, striatal, or cortical injection of recombinant IL-1β at the onset of permanent middle cerebral artery occlusion in the rat. Intracerebroventricular injection of IL-1β (2.5 ng) significantly increased infarct volume in the striatum (35%, P < 0.0001) and in the cortex (44%, P < 0.0001) compared with vehicle treatment. Direct injection of IL-1β into the striatum also increased infarct volume in both the striatum (36%, P < 0.0001) and the cortex (38%, P < 0.0001), whereas injection of IL-1β into the cortex failed to affect infarct volume in either the striatum or the cortex. Cortical injection of a higher dose of IL-1β (20 ng) also failed to affect ischemic damage in either the striatum or the cortex. Injection of IL-1β into the striatum contralateral to the infarction had no effect on striatal damage in the ischemic hemisphere, but did increase cortical damage by 18% ( P < 0.0001). In separate groups of animals, IL-1β (2.5 ng) was injected into either the striatum or the cortex, and body temperature was recorded continuously in conscious free-moving animals by remote telemetry. Injection of IL-1β at either site failed to influence body temperature, suggesting that exacerbation of brain damage by striatal injection of IL-1β is not caused by effects on body temperature. These results imply that IL-1β exacerbates ischemic damage by specific actions in the striatum where it can influence damage at distant sites in the cortex.
Bcl-x1 Bax Interaction after Transient Global Ischemia
Authors: Antonawich Francis J. , Krajewski Stanislaw , Reed John C. , Davis James N.
Published: November 2003

Five minutes of bilateral common carotid artery occlusion in the Mongolian gerbil results in a selective, delayed death of CA1 pyramidal neurons. Although Bcl-2 appears to protect a variety of cells from cell death, the precise role of this apoptosis-regulating protein is complicated. We used immunoblots to estimate levels of Bcl-2, Bcl-xl, and Bax at various times after carotid occlusion. Rather than Bcl-2, Bcl-xl appears to be the predominant neuroprotective form of this family of proto-oncogenes in the gerbil hippocampus. After transient ischemia, Bcl-2 and Bcl-xl protein levels remained the same. However, Bax levels were dramatically increased at 6 hours after ischemia, compared with sham-operated animals, and were still elevated at 72 hours after ischemia. To monitor dimerization interactions among theses apoptosis-regulating molecules, immunoprecipitation studies were conducted. These studies demonstrated that Bcl-xl association with Bax increases after ischemia. Therefore, Bax may disrupt the more favorable Bcl-xl (Bcl-2) interactions necessary for normal neuronal functioning and thus promote transient ischemic death.
Noninvasive Detection of Cerebral Hypoperfusion and Reversible Ischemia from Reductions in the Magnetic Resonance Imaging Relaxation Time, T2
Authors: Gröhn Olli H. J. , Lukkarinen Jouko A. , Oja Joni M. E. , van Zijl Peter C. M. , Ulatowski John A. , Traystman Richard J. , Kauppinen Risto A.
Published: November 2003

The hypothesis was tested that hypoperfused brain regions, such as the ischemic penumbra, are detectable by reductions in absolute transverse relaxation time constant ( T2) using magnetic resonance imaging (MRI). To accomplish this, temporal evolution of T2 was measured in several models of hypoperfusion and focal cerebral ischemia in the rat at 9.4 T. Occurrence of acute ischemia was determined through the absolute diffusion constant Dav = 1/3Trace [double overline] D, while perfusion was assessed by dynamic contrast imaging. Three types of regions at risk of infarction could be distinguished: (1) areas with reduced T2 (4% to 15%, all figures relative to contralateral hemisphere) and normal Dav, corresponding to hypoperfusion without ischemia; (2) areas with both reduced T2 (4% to 12%) and Dav (22% to 49%), corresponding to early hypoperfusion with ischemia; (3) areas with increased T2 (2% to 9%) and reduced Dav (28% to 45%), corresponding to irreversible ischemia. In the first two groups, perfusion-deficient regions detected by bolus tracking were similar to those with initially reduced T2. In the third group, bolus tracking showed barely detectable arrival of the tracer in the region where Dav was reduced. We conclude that T2 reduction in acute ischemia can unambiguously identify regions at risk and potentially discriminate between reversible and irreversible hypoperfusion and ischemia.
Enhanced Poly(ADP-ribosyl)ation after Focal Ischemia in Rat Brain
Authors: Tokime Tomoo , Nozaki Kazuhiko , Sugino Toshiyuki , Kikuchi Haruhiko , Hashimoto Nobuo , Ueda Kunihiro
Published: November 2003

Nitric oxide from neuronal cells plays detrimental roles in glutamate neurotoxicity and in focal brain ischemia. Nitric oxide directly damages DNA, and breaks in the DNA strands activate poly(ADP-ribose) polymerase (PARP), which brings poly(ADP-ribosyl)ation of the nuclear proteins. The excessive activation of PARP is thought to cause depletion of ATP and the energy failure resulting in cell death. To clarify the involvement of poly(ADP-ribosyl)ation in ischemic insult, we examined poly(ADP ribosyl)ation by immunohistochemical methods and the protective effect of 3-aminobenzamide, which is a PARP inhibitor, on focal brain ischemia using an intraluminal permanent middle cerebral artery occlusion model in rats. Poly(ADP ribosyl)ation was widely and markedly detected 2 hours after the ischemic insult in the cerebral cortex and striatum in which infarction developed 24 hours later. The enhanced immunoreactivity of poly(ADP-ribose) gradually decreased, and 16 hours later, no immunoreactivity was detected. Intraventricular administration of 3-aminobenzamide (1 to 30 mg/kg) 30 minutes before the ischemic insult decreased infarction volume in a dose-dependent manner along with the immunohistochemical reduction of poly(ADP-ribosyl)ation. Pretreatment with 7-nitroindazole (25 mg/kg, intraperitoneally), a selective neuronal nitric oxide synthetase inhibitor, partially reduced poly(ADP-ribosyl)ation. These data suggest the involvement of poly(ADP-ribosyl)ation in the development of cerebral infarction.
Polynitroxyl Albumin Reduces Infarct Size in Transient Focal Cerebral Ischemia in the Rat: Potential Mechanisms Studied by Magnetic Resonance Imaging
Authors: Beaulieu Christian , Busch Elmar , Röther Joachim , de Crespigny Alexander , Hsia Carleton J. C. , Moseley Michael E.
Published: November 2003

Nitroxide free radicals are known to protect cells from oxidative damage. Diffusion-weighted and perfusion-weighted magnetic resonance imaging was used to evaluate the effects of polynitroxyl albumin(PNA) in a middle cerebral artery intraluminal suture model of transient focal cerebral ischemia in the rat. Three groups of Sprague-Dawley rats were investigated: (1) PNA(N = 6), (2) human serum albumin (N = 6), and (3) saline (N = 7). The middle cerebral artery was occluded for 2 hours. Treatment was started 30 minutes after induction of ischemia. A total dose of 1% body weight (volume/weight) of PNA (23.5 mg/dL protein and 110 mmol/L nitroxide), albumin (23.5 mg/dL), or saline was injected intravenously at three time points: 0.5% at 0.5 hours, 0.25% at 2 hours (i.e., just before reperfusion), and 0.25% at 4 hours after occlusion. Six sets of diffusion- and perfusion-weighted magnetic resonance images were acquired throughout the 2 hours of ischemia and the 2 hours of reperfusion. The rats were killed at 24 hours, and the brains were stained with 2,3,5-triphenyltetrazolium chloride (TTC). Diffusion-weighted imaging showed that the growth of the ischemic lesion was suppressed in the PNA-treated group. The 4 hours diffusion-weighted imaging-derived hemispheric lesion volume in the PNA-treated group (25% ± 9%) was significantly smaller than that in the saline-treated(43% ± 13%; P = 0.016) or albumintreated groups (38% ± 6%; P = 0.017). A larger difference was observed for the 24-hour TTC-derived lesion volumes in the PNA (8% ± 7%), saline (35% ± 8%; P< 0.001), and albumin (31% ± 6%; P < 0.001) groups. Perfusion-weighted imaging demonstrated a marked improvement in cerebral perfusion in the PNA-treated group during ischemia and reperfusion. In conclusion, treatment with PNA results in an improvement in perfusion and a reduction of infarct volume in a model of transient focal cerebral ischemia in the rat.
Assessment of Dynamic Neurotransmitter Changes with Bolus or Infusion Delivery of Neuroreceptor Ligands
Authors: Endres Christopher J. , Carson Richard E.
Published: November 2003

To describe the effect of endogenous dopamine on [11C]raclopride binding, we previously extended the conventional receptor ligand model to include dynamic changes in neurotransmitter concentration. Here, we apply the extended model in simulations of neurotransmitter competition studies using either bolus or bolus-plus-infusion (B/I) tracer delivery. The purpose of this study was (1) to develop an interpretation of the measured change in tracer binding in terms of underlying neurotransmitter changes, and (2) to determine tracer characteristics that maximize sensitivity to neurotransmitter release. A wide range of kinetic parameters was tested based on existing reversible positron emission tomography tracers. In simulations of bolus studies, the percent reduction in distribution volume (Δ V) caused by a neurotransmitter pulse was calculated. For B/I simulations, equilibrium was assumed, and the maximum percent reduction in tissue concentration (Δ C) after neurotransmitter release was calculated. Both Δ V and Δ C were strongly correlated with the integral of the neurotransmitter pulse. The values of Δ V and Δ C were highly dependent on the kinetic properties of the tracer in tissue, and Δ V could be characterized in terms of the tissue free tracer concentration. The value of Δ V was typically maximized for binding potentials of ~3 to 10, with Δ C being maximized at binding potentials of ~1 to 2. Both measures increased with faster tissue-to-blood clearance of tracer and lower nonspecific binding. These simulations provide a guideline for interpreting the results of neurotransmitter release studies and for selecting radiotracers and experimental design.
Tissue at Risk of Infarction Rescued by Early Reperfusion: A Positron Emission Tomography Study in Systemic Recombinant Tissue Plasminogen Activator Thrombolysis of Acute Stroke
Authors: Heiss Wolf-Dieter , Grond Martin , Thiel Alexander , von Stockhausen Hans-Martin , Rudolf Jobst , Ghaemi Mehran , Löttgen Jan , Stenzel Christoph , Pawlik Gunter
Published: November 2003

Thrombolytic therapy of acute ischemic stroke can be successful only as long as there is penumbral tissue perfused at rates between the thresholds of normal function and irreversible structural damage, respectively. To determine the proportion of tissue at risk of infarction, cerebral perfusion was studied in 12 patients with acute ischemic stroke who underwent treatment with systemic recombinant tissue plasminogen activator (0.9 mg/kg body weight according to National Institute of Neurological Disorders and Stroke protocol) within 3 hours of onset of symptoms, using [15O]-H2O positron emission tomography (PET) before or during, and repeatedly after thrombolysis. The size of the regions of critically hypoperfused gray matter were identified on the initial PET scans, and changes of perfusion in those areas were related to the clinical course (followed by the National Institutes of Health stroke scale) and to the volume of infarcted gray matter demarcated on magnetic resonance imaging 3 weeks after the stroke. Whereas the initial clinical score was unrelated to the size of the ischemic area, after 3 weeks there was a strong correlation between clinical deficit and volume size of infarcted gray matter (Spearman's rho, 0.96; P < 0.001). All patients with a severely hypoperfused (< 12 mL/100 g/min) gray matter region measuring less than 15 mL on first PET showed full morphologic and clinical recovery (n = 5), whereas those with ischemic areas larger than 20 mL developed infarction and experienced persistent neurologic deficits of varying degree. Infarct sizes, however, were smaller than expected from previous correlative PET and morphologic studies of patients with acute stroke: only 22.7% of the gray matter initially perfused at rates below the conventional threshold of critical ischemia became necrotic. Actually, the percentage of initially ischemic voxels that became reperfused at almost normal levels clearly predicted the degree of clinical improvement achieved within 3 weeks. These sequential blood flow PET studies demonstrate that critically hypoperfused tissue can be preserved by early reperfusion, perhaps related to thrombolytic therapy. The results correspond with experimental findings demonstrating the prevention of large infarcts by early reperfusion to misery perfused but viable tissue.
An Adiabatic Approximation to the Tissue Homogeneity Model for Water Exchange in the Brain: I. Theoretical Derivation
Authors: Lawrence Keith S. St. , Lee Ting-Yim
Published: November 2003

Using the adiabatic approximation, which assumes that the tracer concentration in parenchymal tissue changes slowly relative to that in capillaries, we derived a time-domain, closed-form solution of the tissue homogeneity model. This solution, which is called the adiabatic solution, is similar in form to those of two-compartment models, Owing to its simplicity, the adiabatic solution can be used in CBF experiments in which kinetic data with only limited time resolution or signal-to-noise ratio, or both, are obtained. Using computer simulations, we investigated the accuracy and the precision of the parameters in the adiabatic solution for values that reflect 2H-labeled water (D2O) clearance from the brain (see Part II). It was determined that of the three model parameters, (1) the vascular volume ( Vi), (2) the product of extraction fraction and blood flow ( EF), and (3) the clearance rate constant ( kadb), only the last one could be determined accurately, and therefore CBF must be determined from this parameter only. From the error analysis of the adiabatic solution, it was concluded that for the D2O clearance experiments described in Part II, the coefficient of variation of CBF was approximately 7% in gray matter and 22% in white matter.
The Cerebral Metabolic Consequences of Nitric Oxide Synthase Deficiency: Glucose Utilization in Endothelial and Neuronal Nitric Oxide Synthase Null Mice
Authors: Browne Susan E. , Ayata Cenk , Huang Paul L. , Moskowitz Michael A. , Beal M. Flint
Published: November 2003

Nitric oxide has multiple physiologic roles in the CNS. Inhibiting nitric oxide synthesis might therefore alter functional activity within the brain. We used [14C]-2-deoxyglucose in vivo autoradiography to measure local CMRglc in “knockout” mice lacking the genes for either the endothelial (eNOS) or neuronal (nNOS) isoforms of nitric oxide synthase, and in the progenitor strains (SV129, CS7B1/6). Glucose utilization levels did not significantly differ between nNOS and eNOS knockout mice and C57B1/6 mice in any of the 48 brain regions examined, but were relatively lower in some subcortical regions in SV129 mice.
Oxygen Consumption of Cerebral Cortex Fails to Increase during Continued Vibrotactile Stimulation
Authors: Fujita Hitoshi , Kuwabara Hiroto , Reutens David C. , Gjedde Albert
Published: November 2003

The coupling of oxidative metabolism to the blood flow of the sensory motor hand area is uncertain. The authors tested the hypothesis that continued vibrotactile stimulation ultimately must lead to increased oxygen consumption consumption. Twenty-two healthy right-handed young volunteers underwent positron emission tomography (PET) with the [15O]water bolus injection method to measure water clearance ( K H2 O1 an index of blood flow (CBF), and with the [15O]oxygen bolus inhalation method to measure CMR O2. The CMR O2 was measured 30 seconds and 20 minutes after onset of intermittent (1 second on, 1 second off) vibrotactile stimulation (110 Hz) and compared with baseline measurements without stimulation. The K H2 O1 and CMR O2 changes (Δ K H2 O1 and Δ CMR O2) were determined using intersubject averaging, together with magnetic resonance imaging based stereotaxic registration technique. The K H2 O1 increase was 21 ± 4% and 12 ± 4% at 30 seconds and 20 minutes after onset of stimulation, respectively. No significant increase of CMR O2 was found until 30 minutes after the onset of stimulation. The authors conclude that blood flow and oxidative metabolism undergo uncoupling during sustained phasic stimulation of the sensory hand area. Therefore, neuronal activity stimulated in this manner does not rely on significantly increased oxidative phosphorylation.
Differential Expressions of Glycine Transporter 1 and Three Glutamate Transporter mRNA in the Hippocampus of Gerbils with Transient Forebrain Ischemia
Authors: Fujita Hiroko , Sato Kohji , Wen Tong-Chun , Peng Yi , Sakanaka Masahiro
Published: November 2003

The extracellular concentrations of glutamate and its co-agonist for the N-methyl-d-aspartate (NMDA) receptor, glycine, may be under the control of amino acid transporters in the ischemic brain, However, there is little information on changes in glycine and glutamate transporters in the hippocampal CA1 field of gerbils with transient forebrain ischemia. This study investigated the spatial and temporal expressions of glycine transporter 1 (GLYT 1) and three glutamate transporter (excitatory amino acid carrier 1, EAAC 1; glutamate/aspartate transporter, GLAST; glutamate transporter 1, GLT1) mRNA in the gerbil hippocampus after 3 minutes of ischemia. The GLYT1 mRNA was transiently upregulated by the second day after ischemia in astrocytelike cells in close vicinity to hippocampal CA1 pyramidal neurons, possibly to reduce glycine concentration in the local extracellular spaces. The EAAC1 mRNA was abundantly expressed in almost all pyramidal neurons and dentate granule cells in the control gerbil hippocampus, whereas the expression level in CA1 pyramidal neurons started to decrease by the fourth day after ischemia in synchrony with degeneration of the CA1 neurons. The GLAST and GLT1 mRNA were rather intensely expressed in the dentate gyrus and CA3 field of the control hippocampus, respectively, but they were weakly expressed in the CA1 field before and after ischemia. As GLAST and GLT1 play a major role in the control of extracellular glutamate concentration, the paucity of these transporters in the CA1 field may account for the vulnerability of CA1 neurons to ischemia, provided that the functional GLAST and GLT1 proteins are also less in the CA1 field than in the CA3 field. This study suggests that the amino acid transporters play pivotal roles in the process of delayed neuronal death in the hippocampal CA1 field.
Neurofilament Proteolysis after Focal Ischemia; When Do Cells Die after Experimental Stroke?
Authors: Aronowski Jaroslaw , Cho Ki-Hyun , Strong Roger , Grotta James C.
Published: November 2003

To determine the occurrence and time-course of presumably irreversible subcellular damage after moderate focal ischemia, rats were subjected to 1, 3, 6, 9, or 24 hours of permanent unilateral middle cerebral and common carotid occlusion or 3 hours of reversible occlusion followed by 3, 6, or 21 hours of reperfusion. The topography and the extent of damage were analyzed with tetrazolium staining and immunoblot using an antibody capable of detecting breakdown of neurofilament. Neurofilament proteolysis began after 3 hours in the infarct core but was still incomplete in penumbral regions up to 9 hours. Similarly, tetrazolium-staining abnormalities were observed in the core of 50% of animals after 3 hours of ischemia. At 6 hours of permanent ischemia, infarct volume was maximal, and further prolongation of occlusion to 9 or 24 hours did not increase abnormal tetrazolium staining. In contrast to permanent ischemia and in agreement with the authors' previous demonstration of “reperfusion injury” in this model, prolongation of reperfusion from 3 hours to 6 and 21 hours after 3 hours of reversible occlusion gradually augmented infarct volume by 203% and 324%, respectively. Neurofilament proteolysis initiated approximately 3 hours after ischemia was quantitatively greatest in the core and extended during reperfusion to incorporate penumbra with a similar time course to that of tetrazolium abnormalities. These data demonstrate that, at least as measured by neurofilament breakdown and mitochondrial failure, extensive cellular damage is not present in penumbral regions for up to 9 hours, suggesting the potential for rescuing these regions by appropriate and timely neuroprotective strategies.
Modeling Cerebral Blood Flow and Flow Heterogeneity from Magnetic Resonance Residue Data
Authors: Østergaard Leif , Chesler David A. , Weisskoff Robert M. , Sorensen A. Gregory , Rosen Bruce R.
Published: November 2003

Existing model-free approaches to determine cerebral blood flow by external residue detection show a marked dependence of flow estimates on tracer arrival delays and dispersion. In theory, this dependence can be circumvented by applying a specific model of vascular transport and tissue flow heterogeneity. The authors present a method to determine flow heterogeneity by magnetic resonance residue detection of a plasma marker. Probability density functions of relative flows measured in six healthy volunteers were similar among tissue types and volunteers, and were in qualitative agreement with literature measurements of capillary red blood cell and plasma velocities. Combining the measured flow distribution with a model of vascular transport yielded excellent model fits to experimental residue data. Fitted gray-to-white flow-rate ratios were in good agreement with PET literature values, as well as a model-free singular value decomposition (SVD) method in the same subjects. The vascular model was found somewhat sensitive to data noise, but showed far less dependence on vascular delay and dispersion than the model-free SVD approach.
Blockade of the Mitochondrial Permeability Transition Pore Diminishes Infarct Size in the Rat after Transient Middle Cerebral Artery Occlusion
Authors: Matsumoto Shohei , Friberg Hans , Ferrand-Drake Michel , Wieloch Tadeusz
Published: November 2003

The mitochondrial permeability transition pore is an inducer of cell death. During the reperfusion phase after cerebral ischemia, calcium accumulates in mitochondria, and a burst of free radical formation occurs, conditions that favor the activation of the mitochondrial permeability transition pore. Here the authors demonstrate that a blocker of the mitochondrial permeability transition pore, the nonimmunosuppressive cyclosporin A analogue N-methyl-Val-4-cyclosporin A (10 mg/kg intraperitoneally), administered during reperfusion and at 24 hours of reperfusion, diminishes infarct size in a rat model of transient focal ischemia of 2 hours' duration. The mitochondrial permeability transition pore may be an important target for drugs against stroke.
Inflammatory Mediators and Stroke: New Opportunities for Novel Therapeutics
Authors: Barone Frank C. , Feuerstein Giora Z.
Published: November 2003

Contrary to previous dogmas, it is now well established that brain cells can produce cytokines and chemokines, and can express adhesion molecules that enable an in situ inflammatory reaction. The accumulation of neutrophils early after brain injury is believed to contribute to the degree of brain tissue loss. Support for this hypothesis has been drawn from many studies where neutrophil-depletion blockade of endothelial-leukocyte interactions has been achieved by various techniques. The inflammation reaction is an attractive pharmacologic opportunity, considering its rapid initiation and progression over many hours after stroke and its contribution to evolution of tissue injury. While the expression of inflammatory cytokines that may contribute to ischemic injury has been repeatedly demonstrated, cytokines may also provide “neuroprotection” in certain conditions by promoting growth, repair, and ultimately, enhanced functional recovery. Significant additional basic work is required to understand the dynamic, complex, and time-dependent destructive and protective processes associated with inflammation mediators produced after brain injury. The realization that brain ischemia and trauma elicit robust inflammation in the brain provides fertile ground for discovery of novel therapeutic agents for stroke and neurotrauma. Inhibition of the mitogen-activated protein kinase (MAPK) cascade via cytokine suppressive anti-inflammatory drugs, which block p38 MAPK and hence the production of interleukin-1 and tumor necrosis factor-α, are most promising new opportunities. However, spatial and temporal considerations need to be exercised to elucidate the best opportunities for selective inhibitors for specific inflammatory mediators.
Simultaneous Blood Oxygenation Level-Dependent and Cerebral Blood Flow Functional Magnetic Resonance Imaging during Forepaw Stimulation in the Rat
Authors: Silva Afonso C. , Lee Sang-Pil , Yang Guang , Iadecola Costantino , Kim Seong-Gi
Published: November 2003

The blood oxygenation level-dependent (BOLD) contrast mechanism can be modeled as a complex interplay between CBF, cerebral blood volume (CBV), and CMRO2. Positive BOLD signal changes are presumably caused by CBF changes in excess of increases in CMRO2. Because this uncoupling between CBF and CMRO2 may not always be present, the magnitude of BOLD changes may not be a good index of CBF changes. In this study, the relation between BOLD and CBF was investigated further. Continuous arterial spin labeling was combined with a single-shot, multislice echo-planar imaging to enable simultaneous measurements of BOLD and CBF changes in a well-established model of functional brain activation, the electrical forepaw stimulation of a-chloralose-anesthetized rats. The paradigm consisted of two 18- to 30-second stimulation periods separated by a 1-minute resting interval. Stimulation parameters were optimized by laser Doppler flowmetry. For the same cross-correlation threshold, the BOLD and CBF active maps were centered within the size of one pixel (470 µm). However, the BOLD map was significantly larger than the CBF map. Measurements taken from 15 rats at 9.4 T using a 10-millisecond echo-time showed 3.7 ± 1.7% BOLD and 125.67 ± 81.7% CBF increases in the contralateral somatosensory cortex during the first stimulation, and 2.6 ± 1.2% BOLD and 79.3 ± 43.6% CBF increases during the second stimulation. The correlation coefficient between BOLD and CBF changes was 0.89. The overall temporal correlation coefficient between BOLD and CBF time-courses was 0.97. These results show that under the experimental conditions of the current study, the BOLD signal changes follow the changes in CBF.
Effects of the AMPA Receptor Antagonist NBQX on Outcome of Newborn Pigs after Asphyxic Cardiac Arrest
Authors: Brambrink Ansgar M. , Martin Lee J. , Hanley Daniel F. , Becker Kyra J. , Koehler Raymond C. , Traystman Richard J.
Published: November 2003

In neonates, asphyxia is a common cause of neuronal injury and often results in seizures. The authors evaluated whether blockade of a-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors during asphyxia and early recovery with 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo-(F)-quinoxaline (NBQX) ameliorates neurologic deficit and histopathology in 1-week-old piglets. Anesthetized piglets were exposed to a sequence of 30 minutes of hypoxia, 5 minutes of room air ventilation, 7 minutes of airway occlusion, and cardiopulmonary resuscitation. Vehicle or NBQX was administered intravenously before asphyxia (30 mg/kg) and during the first 4 hours of recovery (15 mg/kg/h). Neuropathologic findings were evaluated at 96 hours of recovery by light microscopic and cytochrome oxidase histochemical study. Cardiac arrest occurred at 5 to 6 minutes of airway occlusion, and cardiopulmonary resuscitation restored spontaneous circulation independent of treatment modalities in about 2 to 3 minutes. Neurologic deficit over the 96-hour recovery period was not ameliorated by NBQX. Seizure activity began after 24 to 48 hours in 7 of 10 animals with vehicle and in 9 of 10 of animals with NBQX. In each group, four animals died in status epilepticus. Neuropathologic outcomes were not improved by NBQX. The density of remaining viable neurons was decreased in parietal cortex and putamen by NBQX treatment. Metabolic defects in cytochrome oxidase activity were worsened by NBQX treatment. Seizure activity during recovery was associated with reduced neuronal viability in neocortex and striatum in piglets from both groups that survived for 96 hours. This neonatal model of asphyxic cardiac arrest and resuscitation generates neurologic deficits, clinical seizure activity, and selective damage in regions of basal ganglia and sensorimotor cortex. In contrast to other studies in mature brain, AMPA receptor blockade with NBQX failed to protect against neurologic damage in the immature piglet and worsened postasphyxic histopathologic outcome in neocortex and putamen.
Insulin Induces Dephosphorylation of Eukaryotic Initiation Factor 2α and Restores Protein Synthesis in Vulnerable Hippocampal Neurons after Transient Brain Ischemia
Authors: Sullivan Jonathon M. , Alousi Sarah S. , Hikade Katie R. , Bahu Nabil J. , Rafols José A. , Krause Gary S. , White Blaine C.
Published: November 2003

Brain reperfusion causes prompt, severe, and prolonged protein synthesis suppression and increased phosphorylation of eukaryotic initiation factor 2α [eIF2α(P)] in hippocampal CA1 and hilar neurons, The authors hypothesized that eIF2α(P) dephosphorylation would lead to recovery of protein synthesis. Here the effects of insulin, which activates phosphatases, were examined by immunostaining for eIF2α(P) and autoradiography of in vivo35S amino acid incorporation. Rats resuscitated from a 10-minute cardiac arrest were given 0, 2, 10 or 20U/kg of intravenous insulin, underwent reperfusion for 90 minutes, and were perfusion fixed. Thirty minutes before perfusion fixation, control and resuscitated animals received 500 μCi/kg of 35S methionine/cysteine. Alternate 30-μm brain sections were autoradiographed or immunostained for eIF2α(P). Controls had abundant protein synthesis and no eIF2α(P) in hippocampal neurons. Untreated reperfused neurons in the CA1, hilus, and dentate gyrus had intense staining for eIF2α(P) and reduced protein synthesis; there was little improvement with treatment with 2 or 10 U/kg of insulin. However, with 20 U/kg of insulin, these neurons recovered protein synthesis and were free of eIF2α(P). These results show that the suppression of protein synthesis in the reperfused brain is reversible; they support a causal association between eIF2α(P) and inhibition of protein synthesis, and suggest a mechanism for the neuroprotective effects of insulin.
Hypoglycemic Brain Injury: Potentiation from Respiratory Depression and Injury Aggravation from Hyperglycemic Treatment Overshoots
Authors: de Courten-Myers Gabrielle M. , Xi Guohua , Hwang Jong-Hee , Dunn R. Scott , Mills Ashley S. , Holland Scott K. , Wagner Kenneth R. , Myers Ronald E.
Published: November 2003

Hypoglycemia can cause brain dysfunction, brain injury, and death. The present study seeks to broaden current information regarding mechanisms of hypoglycemic brain injury by investigating a novel etiology. The cat's high resistance to brain injury from hypoglycemia suggested that additional influences such as respiratory depression might play a facilitating role. Three groups of cats were exposed to fasting and insulin-induced hypoglycemia (HG; n = 6), euglycemic respiratory depression (RD; n = 5), and combined hypoglycemic respiratory depression (HG/RD; n = 10). The HG animals were maintained at < 1.5 mmol (mean 1 mmol) serum glucose concentration for 2 to 6.6 hours. The respiratory depression was associated with Pao2 and Paco2 values of ~50 mm Hg for 1 hour and of ~35 and ~75 mm Hg, respectively, for the second hour. Magnetic resonance diffusion-weighted imaging estimated brain energy state before, during, and after hypoglycemia. The hypoglycemic respiratory depression exposures were terminated either to euglycemia (n = 4) or to hyperglycemia (n = 6). Brain injury was assessed after 5 to 7 days of survival. Cats exposed to hypoglycemia alone maintained unchanged diffusion coefficients; that is, they lacked evidence of brain energy failure and all six remained brain-intact. Only 1 of 5 euglycemic RD but 10 of 10 HG/RD cats developed brain damage (HG and RD vs. HG/RD, P < 0.01). This difference in brain injury rates suggests injury potentiation by hypoglycemia and respiratory depression acting together. Three injury patterns emerged, including activation of microglia, selective neuronal necrosis, and laminar cortical necrosis. Widespread activation of microglia suggesting damage to neuronal cell processes affected all damaged brains. Selective neuronal necrosis affecting the cerebral cortex, hippocampus, and basal ganglia was observed in all but one case. Instances of laminar cortical necrosis were limited to cats exposed to hypoglycemic respiratory depression treated with hyperglycemia. Thus, treatment with hyperglycemia compared with euglycemia after hypoglycemic respiratory depression exposures significantly increased the brain injury scores (24 ± 6 vs. 13 ± 2 points; P < 0.05). This new experimental hypoglycemia model's contribution lies in recognizing additional factors that critically define the occurrence of hypoglycemic brain injury.
Estrogen Receptor Antagonist ICI182,780 Exacerbates Ischemic Injury in Female Mouse
Authors: Sawada Masahiko , Alkayed Nabil J. , Goto Shozo , Crain Barbara J. , Traystman Richard J. , Shaivitz Amanda , Nelson Randy J. , Hurn Patricia D.
Published: November 2003

Recent findings in animals emphasize that experimental ischemic brain damage can be strikingly reduced by estrogen; however, the neuroprotective mechanisms are not well understood. It was hypothesized that estrogen signaling via cognate estrogen receptors (ERs) within the vasculature is an important aspect of cerebral ischemic protection in the female brain, in part by amplifying intraischemic cerebral blood flow (CBF). In the present study, the hypothesis that chronic treatment with the pure ER antagonist ICI182,780 (ICI) would increase ischemic brain damage by a blood flow-mediated mechanism was investigated. Adult C57Bl/6J mice were pretreated with either subcutaneous ICI (100 μg/day) or oil/ ethanol vehicle for 1 week before 2 hours of middle cerebral artery occlusion (MCAO) and 22 hours of reperfusion. End-ischemic regional CBF was evaluated in additional cohorts using [14C]iodoantipyrine autoradiography. Infarction volume as measured by cresyl violet histology was greater in the striatum of ICI-treated females (70 ± 3% of contralateral striatum vs. 40 ± 12% in vehicle-treated females). Cortical injury was not enhanced relative to control animals (39 ± 6% of contralateral cortex in ICI group vs. 27 ± 8% in vehicle-treated group). Physiologic variables and ischemic reduction of the ipsilateral cortical laser-Doppler flow signal were similar between groups. Further, ICI treatment did not alter end-ischemic cortical or striatal CBF. The deleterious effect of ICI was limited to females, as there were no differences in stroke damage or CBF between male treatment groups. These data suggest that estrogen inhibits ischemic brain injury in striatum of the female by receptor-mediated mechanisms that are not linked to preservation of intraischemic CBF.
A New Radiopharmaceutical for the Cerebral Dopaminergic Presynaptic Function: 6-Radioiodinated l-meta-Tyrosine
Authors: Flores Leo Garcia , Kawai Keiichi , Nakagawa Mamoru , Shikano Naoto , Jinnouchi Seishi , Tamura Shozo , Watanabe Katsushi , Kubodera Akiko
Published: November 2003

Geometric isomers of radioiodinated l- meta-tyrosine, 6-[I-125]iodo-and 4-[I-125]iodo-l- meta-tyrosine (6-I-l-mTyr, 4-I-l-mTyr) were separated by high-performance liquid chromatography. Both 6-I- and 4-I-l-mTyr had high energy-dependent brain accumulation. 6-I- and 4-I-l-mTyr were also metabolically stable and were rapidly excreted through the urine. 6-I-l-mTyr had a predilection for the cerebral aromatic l-amino acid decarboxylase (DOPA decarboxylase), the final enzyme of dopamine biosynthesis. 6-Radioiodinated l-mTyr is a new radiopharmaceutical that can be both useful in assessing cerebral amino acid transport mechanism and quantifying metabolically active DOPA decarboxylase.