bluuebunny/crossref_metadata_2025 huggingface dataset:
Increased Cerebral Infarct Volumes in Polyglobulic Mice Overexpressing Erythropoietin
Authors: Wiessner Christoph , Allegrini Peter R. , Ekatodramis Dimitrios , Jewell Ursula R. , Stallmach Thomas , Gassmann Max
Published: November 2003

There is increasing evidence that erythropoietin (Epo) has a protective function in cerebral ischemia. When used for treatment, high Epo plasma levels associated with increases in blood viscosity, however, may counteract beneficial effects of Epo in brain ischemia. The authors generated two transgenic mouse lines that overexpress human Epo preferentially, but not exclusively, in neuronal cells. In mouse line tg21, a fourfold increase of Epo protein level was found in brain only, whereas line tg6 showed a dramatic increase of cerebral and systemic transgene expression resulting in hematocrit levels of 80%. Cerebral blood flow (CBF), as determined by bolus tracking magnetic resonance imaging, was not altered in the tg6 line. The time-to-peak interval for the tracer, however, increased approximately threefold in polyglobulic tg6 mice. Immunohistochemical analysis revealed an increase in dilated vessels in tg6 mice, providing an explanation for unaltered CBF in polyglobulic animals. Permanent occlusion of the middle cerebral artery (pMCAO) led to similar perfusion deficits in wild-type, tg6, and tg21 mice. Compared with wild-type controls, infarct volumes were not significantly smaller (22%) in tg21 animals 24 hours after pMCAO, but were 49% enlarged ( P < 0.05) in polyglobulic tg6 mice. In the latter animals, elevated numbers of Mac-1 immunoreactive cells in infarcted tissue suggested that leukocyte infiltration contributed to enlarged infarct volume. The current results indicate that moderately increased brain levels of Epo in tg21 transgenic mice were not sufficient to provide significant tissue protection after pMCAO. The results with tg6 mice indicate that systemic chronic treatment with Epo associated with elevated hematocrit might deteriorate outcome after stroke either because of the elevated hematocrit or other chronic effects.
The 18F-fluorodeoxyglucose Lumped Constant Determined in Human Brain from Extraction Fractions of 18F-fluorodeoxyglucose and Glucose
Authors: Hasselbalch Steen G. , Holm Søren , Pedersen Hanne S. , Svarer Claus , Knudsen Gitte M. , Madsen Peter L. , Paulson Olaf B.
Published: November 2003

Quantification of regional cerebral glucose metabolism (CMRglc) using positron emission tomography and 18F-fluorodeoxyglucose (PET-FDG) requires knowledge of the correction factor between FDG and glucose net clearance, the FDG lumped constant (LC). Because diverging values for LC have been obtained, the authors reevaluated LC by measuring the ratio of the cerebral net extraction fractions of FDG (E*) and glucose (E) from arteriovenous cerebral measurements. Thirty subjects were studied (mean age = 25 ± 4 years): 12 during a programed infusion of FDG and 18 after a bolus injection of FDG. In the infusion study, LC was calculated as the ratio E*/E. In the bolus study, E* was calculated from the slope of a Patlak–Gjedde plot. Lumped constant was significantly smaller in the infusion study as compared with the bolus study (0.48 ± 0.16 vs. 0.81 ± 0.27, P < 0.001). In 4 subjects studied during continuous FDG infusion for 2.5 hours, LC decreased to 0.36 ± 0.11. These results suggest that the “steady-state” method underestimates LC because E* continues to decline because of significant labeled product. Further, the authors provide evidence for resetting of LC toward a greater value. The subsequent resetting of CMRglc provides a physiologically more meaningful estimate and allows for comparison of CMRglc values between different methodologies.
Protective Effect of Heme Oxygenase-1 Gene Transfer against Oxyhemoglobin-Induced Endothelial Dysfunction
Authors: Eguchi Daihiko , Weiler Deborah , Alam Jawed , Nath Karl , Katusic Zvonimir S.
Published: November 2003

The current study was designed to determine the effect of recombinant heme oxygenase-1 (HO-1) gene expression on endothelial function in cerebral arteries. Isolated canine basilar arteries were exposed ex vivo (30 minutes at 37°C) to an adenoviral vector (1010 PFU/mL, total volume 300 μL) encoding either the HO-1 gene (AdCMVHO-1) or the β-galactosidase (β-Gal) reporter gene (AdCMVβ-Gal). Twenty-four hours after transduction, arterial rings were suspended in organ chamber for isometric force recording. Endothelium-dependent relaxations were obtained in response to bradykinin (10−10 to 10−6 mol/L) during contraction to uridine-5′-triphosphate (UTP; 3 × 10−6 to 3 × 10−5 mol/L). Certain rings were incubated with oxyhemoglobin (OxyHb; 10−5 mol/L) overnight (16 to 18 hours of 24 hours). Expression and localization of recombinant protein were shown by Western blot analysis and immunohistochemistry. Endothelium-dependent relaxation to bradykinin and endothelium-independent relaxation to forskolin (10−9 to 10−5 mol/L) and DEA-NONOate (10−10 to 10−5 mol/L) were identical in β-Gal– and HO-1–transduced arteries. Exposure to OxyHb caused impairment of endothelium-dependent relaxation to bradykinin ( P < 0.01). In contrast, OxyHb did not affect endothelium-dependent relaxation in arteries expressing recombinant HO-1 ( P > 0.05). This protective effect of HO-1 was reversed by coincubation with tin protoporphyrin (SnPP9; 10−5 mol/L), a selective inhibitor of HO-1 ( P < 0.01). Basal levels of 3′,5′-cyclic monophosphate (cGMP) in HO-1–transduced vessels were not significantly different from those in β-Gal–transduced vessels. Pretreatment with OxyHb significantly reduced cGMP level in β-Gal–transduced rings ( P < 0.01), whereas it had no effect in HO-1–transduced rings. These results demonstrate that HO-1 gene transfer does not affect endothelial and smooth muscle function of normal arteries, and that expression of recombinant HO-1 in cerebral arteries protects vasomotor function against OxyHb-induced injury.
Three-Dimensional Pulsatile Flow Simulation before and after Endovascular Coil Embolization of a Terminal Cerebral Aneurysm
Authors: Groden Christoph , Laudan Jochen , Gatchell Scott , Zeumer Herrmann
Published: November 2003

The effect of different percentages of coil mesh in a cerebral aneurysm on the pulsatile flow and pressure in the parent vessel and aneurysm lumen was evaluated. Geometric data on a basilar tip aneurysm and vertebrobasilar arteries after subarachnoid hemorrhage was obtained by computer tomographic angiography. Intraarterial pressure was measured at four vertebrobasilar points before and after treatment with detachable coils. Pulsatile flow was documented by transcranial ultrasonography. A three-dimensional computer simulation was created using a commercial fluid dynamics solver for four aneurysm conditions: (1) before intervention; (2) with a 20% filling showing a complete cessation of the inflow through the aneurysm neck; (3) with a 12% filling showing an incomplete deceleration of inflow through the aneurysm neck, with a remaining flow around the embedded platinum coils; and (4) with a 12% filling and simulation of clotted aneurysm dome, which did not inhibit persisting flow phenomena. The relative pressure amplitudes neither increased nor decreased under the different simulated aneurysm filling conditions. Inserted platinum coils can immediately and decisively relieve the influx of pulsating blood and allow for initial clotting. To reach this effect, a volume density of 20% platinum coil mesh in the aneurysm neck is needed.
Blood–Brain Barrier Disruption in White Matter Lesions in a Rat Model of Chronic Cerebral Hypoperfusion
Authors: Ueno Masaki , Tomimoto Hidekazu , Akiguchi Ichiro , Wakita Hideaki , Sakamoto Haruhiko
Published: November 2003

Blood–brain barrier damage has been implicated in the pathogenesis of cerebrovascular white matter lesions. This type of lesion is responsible for cognitive impairment in the elderly and can be induced by permanent ligation of the bilateral common carotid arteries in the rat. Because it is unclear whether the blood–brain barrier is impaired, we examined whether vascular permeability to horseradish peroxidase is altered using this model. According to light microscopic results, the reaction product of horseradish peroxidase was most intensely localized to the paramedian part of the corpus callosum in the brain, occurring to a small degree at 3 hours, day 1, markedly on day 3, but reduced on days 7 and 14. By electron microscopic study of the same area, the reaction product of horseradish peroxidase was localized to the plasmalemmal vesicles in the endothelial cells 3 hours after ligation, but appeared in the cytoplasm on days 1 and 3, suggesting a diffuse leakage of horseradish peroxidase. In addition, the reaction product was dispersed into the cytoplasm of glial cells in the perivascular regions on day 3. The luminal surface of the endothelial cell cytoplasm appeared irregular on day 7, suggesting a conformational change of the endothelial cells. Collagen fibrils proliferated in the thickened basal lamina and mitochondria degenerated in the pericyte on days 7 and 14. Perivascular glial endfeet were swollen throughout the survival period. In sham-operated rats, the reaction product of horseradish peroxidase was not observed at any time interval, except in vesicular structures. These findings indicate that chronic cerebral hypoperfusion induces blood–brain barrier damage with subsequent morphologic changes of the vascular structures in the corpus callosum. An extravasation of macromolecules, such as proteases and immunoglobulins, may contribute to the pathogenesis of white matter lesions.
TNF-α–Induced Tolerance to Ischemic Injury Involves Differential Control of NF-κB Transactivation: The Role of NF-κB Association with p300 Adaptor
Authors: Ginis Irene , Jaiswal Rama , Klimanis Dace , Liu Jie , Greenspon Jose , Hallenbeck John M.
Published: November 2003

Preconditioning with sublethal ischemia results in natural tolerance to ischemic stress, where multiple mediators of ischemic damage are simultaneously counteracted. Tumor necrosis factor alpha (TNF-α) has been implicated in development of ischemic tolerance. Using cellular models of ischemic tolerance, we have demonstrated that an effector of TNF-α– induced preconditioning is ceramide, a sphingolipid messenger in TNF-α signaling. TNF-α/ceramide-induced preconditioning protected cultured neurons against ischemic death and cultured astrocytes against proinflammatory effects of TNF-α. TNF-α activates a transcription factor NF-κB that binds promoters of multiple genes, thus ensuring pleiotropic effects of TNF-α. We describe here a mechanism that allows selective suppression of TNF-α/NF-κB–induced harmful genes in preconditioned cells while preserving cytoprotective responses. We demonstrate that in astrocytes activation of an adhesion molecule ICAM-1 by TNF-α is regulated through association of the phosphorylated p65 subunit of NF-κB with an adapter protein, p300, and that in preconditioned cells p65 remains unphosphorylated and ICAM-1 transcription is inhibited. However, TNF-α–activated transcription of a protective enzyme, MnSOD, does not depend on p300 and does not become inhibited in preconditioned cells. This new understanding of TNF-α–induced adaptation to ischemic stress and inflammation could suggest novel avenues for clinical intervention during ischemic and inflammatory diseases.
Local Cerebral Blood Flow during Lithium–Pilocarpine Seizures in the Developing and Adult Rat: Role of Coupling between Blood Flow and Metabolism in the Genesis of Neuronal Damage
Authors: de Vasconcelos Anne Pereira , Ferrandon Arielle , Nehlig Astrid
Published: November 2003

Coupling between local cerebral blood flow and local cerebral metabolic rate for glucose is involved in the pathogenesis of epilepsy-related neuronal damage in the adult brain; however, its role in the immature brain is unknown. Lithium–pilocarpine–induced status epilepticus is associated with extended damage in adult rats, mostly in the forebrain limbic areas and thalamus, whereas damage was moderate in 21-day-old rats (P21) or absent in P10 rats. The quantitative autoradiographic [14C]iodoantipyrine technique was applied to measure the consequences of lithium-pilocarpine status epilepticus on local cerebral blood flow. In adult and P21 rats, local cerebral blood flow rates increased by 50% to 400%; the highest increases were recorded in regions showing damage in adults. At P10, local cerebral blood flow rates decreased by 40% to 60% in most areas, except in some forebrain regions showing no change during status epilepticus. In areas injured when status epilepticus was induced in adults, a strong hypermetabolism ( Fernandes et al., 1999 ) not matched by comparable local cerebral blood flow increases was present in rats of all ages, whereas in damage-resistant areas, local cerebral metabolic rate for glucose and local cerebral blood flow remained coupled in the three age groups. Thus, the level of coupling between blood flow supply and metabolism is not involved in seizure-related brain damage in the developing brain, which appears to be resistant to the consequences of such a mismatch.
Role of Intracellular Calcium Stores in Cell Death from Oxygen–Glucose Deprivation in a Neuronal Cell Line
Authors: Wang Chen , Nguyen Henry N. , Maguire Jamie L. , Perry David C.
Published: November 2003

To determine the role of calcium homeostasis in ischemic neuronal death, the authors used an in vitro model of oxygen–glucose deprivation in neuronal cell lines. Exposure of human neuroblastoma SH-SY5Y cells to 10- to 16-hour oxygen–glucose deprivation decreased viability to 50% or less, and longer exposure times killed almost all cells. The death following 10- to 16-hour oxygen–glucose deprivation was not manifested until 24 to 72 hours after exposure. Deprivation of both glucose and oxygen together was required for expression of toxicity at these exposure times. Dantrolene, which blocks the release of endoplasmic reticulum Ca2+ stores, partially protected SH-SY5Y cells from oxygen–glucose deprivation toxicity. The addition of dantrolene during the deprivation phase alone produced the maximal drug effect; no further protection was obtained by continued drug exposure during the recovery phase. Prevention of Ca2+ influx by chelation or channel blockade or the chelation of cytosolic Ca2+ did not inhibit oxygen-glucose deprivation toxicity. In contrast, increasing extracellular Ca2+ or stimulating Ca2+ influx did inhibit toxicity. Calcium measurements with fura-2 acetoxymethylester revealed that oxygen–glucose deprivation caused a significant reduction in thapsigargin-releasable endoplasmic reticular stores of Ca2+. These studies suggest that an important component of the neuronal toxicity in cerebral ischemia is due to disruption of calcium homeostasis, particularly to the depletion of intracellular Ca2+ stores.
Induction of Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH) Expression in Rat Brain after Focal Ischemia/Reperfusion
Authors: Tanaka Ryota , Mochizuki Hideki , Suzuki Asuka , Katsube Nobuo , Ishitani Ryoichi , Mizuno Yoshikuni , Urabe Takao
Published: November 2003

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a glycolytic enzyme, has been recently identified to be involved in the initiation of neuronal apoptosis. To investigate the serial changes and cellular localization of GAPDH expression, and its role in ischemia/reperfusion-induced neuronal apoptosis, the authors analyzed immunohistochemically brain areas of rats subjected to middle cerebral artery occlusion (MCAO) and reperfusion. Nuclear overexpression of GAPDH was noted in the ischemic core area after 2 hours of MCAO without reperfusion. During the subsequent reperfusion, nuclear accumulation of GAPDH in this area decreased in a time-dependent manner. However, cytoplasmic and nuclear GAPDH immunoreactivity was detected in neurons of the penumbra area of the parietal cortex, in rats subjected to 2-hour MCAO followed by 3-hour reperfusion. The increase of nuclear GAPDH immunoreactivity was persistently noted up to 48 hours of reperfusion, whereas cytoplasmic immunoreactivity correlated inversely with the duration of reperfusion. Moreover, double staining revealed colocalization of nuclear GAPDH and TUNEL in the penumbra area. The authors' study demonstrated that overexpression of GAPDH and nuclear translocation occurred in both the ischemic core and penumbra area soon after focal ischemia. These processes could be viewed as an early marker of ischemia/reperfusion-induced apoptotic neuronal death. The results suggest that GAPDH may play a critical role in the progression and spread of ischemic neuronal damage.
Activation of Mitochondrial ATP-Dependent Potassium Channels Protects Neurons against Ischemia-Induced Death by a Mechanism Involving Suppression of Bax Translocation and Cytochrome c Release
Authors: Liu Dong , Lu Chengbiao , Wan Ruiqian , Auyeung Wendy W. , Mattson Mark P.
Published: November 2003

Neurons express a variety of plasma-membrane potassium channels that play important roles in regulating neuronal excitability and synaptic transmission, but also contain mitochondrial ATP-sensitive potassium channels, the functions of which are unknown. Studies of cardiac cells suggest that similar mitochondrial ATP-sensitive potassium channels are involved in the process of ischemic preconditioning, suggesting a role in regulating cell survival. The authors report that mice given diazoxide, an activator of mitochondrial ATP-sensitive potassium channels, exhibited a large (60% to 70%) decrease in cortical infarct size after permanent occlusion of the middle cerebral artery. Diazoxide decreases neuronal apoptosis and increases astrocyte survival and activation in the penumbral region of the ischemic cortex. The neuroprotective effect of diazoxide is abolished by 5-hydroxydecanoate, a selective antagonist of mitochondrial ATP-sensitive potassium channels. Studies of cultured hippocampal neurons reveal that diazoxide depolarizes mitochondria, prevents cytochrome c release, and protects cells against death induced by staurosporine and chemical hypoxia. Diazoxide increased the levels of Bcl2 and inhibited the association of Bax with mitochondria in neurons exposed to an apoptotic insult, suggesting that activation of mitochondrial ATP-sensitive potassium channels may stabilize mitochondrial function by differentially modulating proapoptotic and anti-apoptotic proteins. Collectively, the data suggest that mitochondrial ATP-sensitive potassium channels play a key role in modulating neuronal survival under ischemic conditions, and identify agents that activate mitochondrial ATP-sensitive potassium channels as potential therapeutics for stroke and related neurodegenerative conditions.
Hematopoietic Factor Erythropoietin Fosters Neuroprotection through Novel Signal Transduction Cascades
Authors: Chong Zhao Zhong , Kang Jing-Qiong , Maiese Kenneth
Published: November 2003

In addition to promoting the survival, proliferation, and differentiation of immature erythroid cells, erythropoietin and the erythropoietin receptor have recently been shown to modulate cellular signal transduction pathways that extend beyond the erythropoietic function of erythropoietin. In particular, erythropoietin has been linked to the prevention of programmed cell death in neuronal systems. Although this work is intriguing, the underlying molecular mechanisms that serve to mediate neuroprotection by erythropoietin are not well understood. Further analysis illustrates that erythropoietin modulates two distinct components of programmed cell death that involve the degradation of DNA and the externalization of cellular membrane phosphatidylserine residues. Initiation of the cascades that modulate protection by erythropoietin and its receptor may begin with the activation of the Janus tyrosine kinase 2 protein. Subsequent downstream mechanisms appear to lead to the activation of multiple signal transduction pathways that include transcription factor STAT5 (signal transducers and activators of transcription), Bcl-2, protein kinase B, cysteine proteases, mitogen-activated protein kinases, proteintyrosine phosphatases, and nuclear factor-κB. New knowledge of the cellular pathways regulated by erythropoietin in neuronal environments will potentially solidify the development and initiation of therapeutic strategies against nervous system disorders.
Microvascular Basal Lamina Injury after Experimental Focal Cerebral Ischemia and Reperfusion in the Rat
Authors: Hamann Gerhard F. , Liebetrau Martin , Martens Helge , Burggraf Dorothe , Kloss Christian U. A. , Bültemeier Gundula , Wunderlich Natalie , Jäger Gabriele , Pfefferkorn Thomas
Published: November 2003

To define the location and extent of microvascular damage of the basal lamina after cerebral ischemia and reperfusion in rats, the authors subjected animals (n = 16) to 3 hours of focal cerebral ischemia and 24 hours of reperfusion using the suture middle cerebral artery occlusion model; sham-operated animals served as controls (n = 6). The Western blot technique was used to define the collagen type IV protein content in various brain regions, whereas immunohistochemistry identified microvascular basal lamina loss (anticollagen type IV staining). The extent of damage was quantified by automatic morphometric video-imaging analysis. Statistical analysis was based on the Mann-Whitney test and the paired Student's t-test. The ischemic hemisphere showed a reduction of the collagen type IV protein content after ischemia and reperfusion in the Western blot (reduction compared with the nonischemic side: total hemisphere, 33% ± 6%; basal ganglia, 49% ± 4%; cortex, 25% ± 7%; P < 0.01). There was also a decrease in the number of cerebral microvessels between the ischemic and nonischemic hemispheres (16% ± 3%), cortical (14% ± 3%), and basal ganglia areas (21% ± 4%) ( P < 0.01). Besides a reduction of the vessel number, there was also a loss in basal lamina antigen-positive stained area in ischemic areas (hemisphere, 20% ± 2%; cortex, 8% ± 3%; basal ganglia, 31% ± 3%; P < 0.001). Cortical areas had a less pronounced basal lamina loss than basal ganglia ( P < 0.05). For the first time, microvascular basal lamina damage, indicated by collagen type IV loss, is proven in rats by biochemical and morphometric analysis. These changes are comparable with those found in nonhuman primates. The authors report novel data regarding microvascular ischemic changes in the cortex. These data provide a basis for future experiments to determine the mechanisms of ischemic microvascular damage and to devise new therapeutic strategies.
Delayed Anoxic Depolarizations in Hippocampal Neurons of Mice Lacking the Excitatory Amino Acid Carrier 1
Authors: Gebhardt Christine , Körner Rafael , Heinemann Uwe
Published: November 2003

Hypoxia leads to a rapid increase in vesicular release of glutamate. In addition, hypoxic glutamate release might be caused by reversed operation of neuronal glutamate transporters. An increase in extracellular glutamate concentration might be an important factor in generating anoxic depolarizations (AD) and subsequent neuronal damage. To study the AD and the vesicular release in hippocampal slices from CD1 wild-type mice and mice in which the neuronal glutamate transporter excitatory amino acid carrier 1 (EAAC1) had been knocked out, the authors performed recordings of field potentials and patch clamp recordings of CA1 pyramidal cells. Latency to anoxic depolarizations was enhanced in EAAC1−/− mice, whereas the hypoxia-induced increase in miniature excitatory postsynaptic current frequency occurred with similarly short latencies and to a similar extent in control and mutated animals. Additional block of glial glutamate uptake with TBOA (dl-threo-β-benzyloxyaspartate), a nontransportable and potent inhibitor, dramatically reduced the latency to onset of AD and abolished the difference between wild-type mice and EAAC1−/− mice. The authors conclude that the neuronal glutamate transporter greatly influences the latency to generation of AD. Because ADs are not prevented in EAAC1-deficient mice, vesicular release mechanisms also seem to be involved. They become prominent when glial glutamate transport is blocked.
TACE/ADAM17–TNF-α Pathway in Rat Cortical Cultures after Exposure to Oxygen–Glucose Deprivation or Glutamate
Authors: Hurtado Olivia , Lizasoain Ignacio , Fernández-Tomé Paz , Álvarez-Barrientos Alberto , Leza Juan C. , Lorenzo Pedro , Moro María A.
Published: November 2003

The role of the tumor necrosis factor (TNF)-α convertase (TACE/ADAM17) in the adult nervous system remains poorly understood. The authors have previously demonstrated that TACE is upregulated in rat forebrain slices exposed to oxygen–glucose deprivation (OGD). They have now used rat mixed cortical cultures exposed to OGD or glutamate to study (1) TACE expression and localization, and (2) the effects of TNF-α release on cell viability. OGD- or glutamate-caused TNF-α release, an effect that was blocked by the TACE inhibitor BB3103 (BB) (0.1–1 μmol/L; control: 1.67 ± 0.59; OGD: 6.59 ± 1.52; glutamate: 3.38 ± 0.66; OGD ± BB0.1: 3.23 ± 0.67; OGD ± BB1: 1.33 ± 0.22 pg/mL, n = 6, P < 0.05). Assay of TACE activity as well as Western blot showed that TACE expression is increased in OGD- or glutamate-exposed cells. In control cultures, TACE immunoreactivity was present in some microglial cells, whereas, after OGD or glutamate, TACE immunostaining appeared in most microglial cells and in some astrocytes. Conversely, BB3103 (0.1 μmol/L) caused apoptosis after glutamate exposure as shown by annexin and Hoechst 33342 staining and caspase-3 activity, an effect mimicked by the proteasome inhibitor MG-132 (caspase activity: glutamate: 5.1 ± 0.1; glutamate + BB: 7.8 ± 0.8; glutamate + MG: 11.9 ± 0.5 pmol · min−1 mg−1 protein, n = 4, P < 0.05), suggesting that translocation of the transcription factor NF-κB mediates TNF-α–induced antiapoptotic effect. Taken together, these data demonstrate that, in rat mixed neuronal–glial cortical cultures exposed to OGD or glutamate, (1) TACE/ADAM17 activity accounts for the majority of TNF-α shedding, (2) an increase in glial TACE expression contributes to the rise in TNF-α, and (3) TNF-α release in this setting inhibits apoptosis via activation of the transcription factor NF-κB.
Endothelial Nitric Oxide Synthase Pathophysiology after Nonocclusive Common Carotid Artery Thrombosis in Rats
Authors: Danton Gary H. , Prado Ricardo , Truettner Jessie , Watson Brant D. , Dietrich W. Dalton
Published: November 2003

Although vascular dysregulation has been documented in patients with extracranial vascular disease, transient ischemic attacks, and stroke, the pathomechanisms are poorly understood. To model thromboembolic stroke in rats, photochemically induced nonocclusive common carotid artery thrombosis (CCAT) was used to generate a platelet thrombus in the carotid artery of anesthetized rats. After CCAT, platelet aggregates break off the thrombus, travel to the distal cerebral vasculature, damage blood vessels, and cause small infarctions. The authors hypothesized that deficits in the endothelial nitric oxide synthase (eNOS) pathway may be responsible for vascular dysfunction after embolic stroke. To examine the functional status of the eNOS system, they measured eNOS-dependent dilation after CCAT by applying acetylcholine through a cranial window over the middle cerebral artery. The authors also measured eNOS mRNA and protein in the middle cerebral artery to determine whether functional changes were caused by alterations in expression. eNOS-dependent dilation was reduced at 6 hours, elevated at 24 hours, and returned to baseline 72 hours after CCAT. Endothelial nitric oxide synthase mRNA increased at 2 hours and was followed by a rise in protein 24 hours after CCAT. Changes in the eNOS system may account for some of the observed vascular deficits in patients with cerebrovascular disease.
Hemodynamic Response in the Unanesthetized Rat: Intrinsic Optical Imaging and Spectroscopy of the Barrel Cortex
Authors: Berwick Jason , Martin Chris , Martindale John , Jones Myles , Johnston Dave , Zheng Ying , Redgrave Peter , Mayhew John
Published: November 2003

Optical imaging spectroscopy was used to measure the hemodynamic response of somatosensory cortex to stimulation of the whiskers. Responses to brief puffs of air were compared in anesthetized and unanesthetized rats. The hemodynamic response was approximately four times larger in the unanesthetized animal than the corresponding anesthetized animal. In unanesthetized animals, a short-latency (approximately 400 milliseconds) short-duration (approximately 300 milliseconds) hemodynamic startle response was observed. General linear model analysis was used to extract this component from the time series, and revealed an underlying short-latency increase in deoxygenated hemoglobin in response to somatosensory stimulation. It is proposed that anesthesia can have a marked affect on the relation between changes in blood volume and blood flow. This work represents a step in the development of an experimental model that can be used to investigate fundamental neurologic processes in the awake-behaving rodent.
Astrocytic Activation and Delayed Infarct Expansion after Permanent Focal Ischemia in Rats. Part I: Enhanced Astrocytic Synthesis of S-100β in the Periinfarct Area Precedes Delayed Infarct Expansion
Authors: Matsui Toru , Mori Takashi , Tateishi Narito , Kagamiishi Yoshifumi , Satoh Souichi , Katsube Nobuo , Morikawa Eiharu , Morimoto Tadashi , Ikuta Fusahiro , Asano Takao
Published: November 2003

An astrocytic protein S-100β enhances the expression of inducible nitric oxide synthase in cultured astrocytes at micromolar concentrations, leading to nitric oxide-mediated death of cocultured neurons. The present study examined whether S-100β production by reactive astrocytes accumulating within the periinfarct area was related to delayed expansion of infarct volume after permanent middle cerebral artery occlusion in the rat. After rapid increases during the initial 24 hours, the increase of infarct volume then decelerated while maintaining the increasing tendency until 168 hours in this model, attaining a significant difference compared with that at 24 hours. In the periinfarct area, the number of reactive astrocytes expressing both S-100 and glial fibrillary acidic protein, the tissue level of S-100β as measured by the sandwich enzyme-linked immunosolvent assay method using anti-S-100β monoclonal antibody, and the number of terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate-biotin nick end labeling-positive cells were significantly increased preceding the delayed expansion of infarct volume. The CSF concentration of S-100β showed a biphasic increase, presumably reflecting the immediate release from astrocytes within the ischemic core and the subsequent production in reactive astrocytes within the periinfarct area. These results show for the first time that the enhanced synthesis of S-100β by reactive astrocytes participates in the inflammatory responses within the periinfarct area, which may be related to the occurrence of delayed infarct expansion as a major component of the cytokine network.
Correlation between Cerebral Blood Flow, Substrate Delivery, and Metabolism in Head Injury: A Combined Microdialysis and Triple Oxygen Positron Emission Tomography Study
Authors: Hutchinson Peter J. , Gupta Arun K. , Fryer Tim F. , Al-Rawi Pippa G. , Chatfield Doris A. , Coles Jonathan P. , O'Connell Mark T. , Kett-White Rupert , Minhas Pawan S. , Aigbirhio Franklin I. , Clark John C. , Kirkpatrick Peter J. , Menon David K. , Pickard John D.
Published: November 2003

Microdialysis continuously monitors the chemistry of a small focal volume of the cerebral extracellular space. Conversely, positron emission tomography (PET) establishes metabolism of the whole brain, but only for the duration of the scan. The objective of this study was to apply both techniques to head-injured patients simultaneously to assess the relation between microdialysis (glucose, lactate, lactate/pyruvate [L/P] ratio, and glutamate) and PET (cerebral blood flow [CBF], cerebral blood volume, oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen) parameters. Microdialysis catheters were inserted into the frontal cerebral cortex and adipose tissue of the anterior abdominal wall of 17 severely head-injured patients. Microdialysis was performed during PET scans, with regions of interest defined by the location of the microdialysis catheter membrane. An intervention (hyperventilation) was performed in 13 patients. The results showed that combining PET and microdialysis to monitor metabolism in ventilated patients is feasible and safe, although logistically complex. There was a significant relation between the L/P ratio and the OEF (Spearman r = 0.69, P = 0.002). There was no significant relation between CBF and the microdialysis parameters. Moderate short-term hyperventilation appeared to be tolerated in terms of brain chemistry, although no areas were sampled by microdialysis where the OEF exceeded 70%. Hyperventilation causing a reduction of the arterial carbon dioxide tension by 0.9 kPa resulted in a significant elevation of the OEF, in association with a reduction in glucose, but no significant elevation in the L/P ratio or glutamate.
Tricarboxylic Acid Cycle Substrates Prevent PARP-Mediated Death of Neurons and Astrocytes
Authors: Ying Weihai , Chen Yongmei , Alano Conrad C. , Swanson Raymond A.
Published: November 2003

The DNA repair enzyme, poly(ADP-ribose) polymerase-1 (PARP1), contributes to cell death during ischemia/reperfusion when extensively activated by DNA damage. The cell death resulting from PARP1 activation is linked to NAD+ depletion and energy failure, but the intervening steps are not well understood. Because glycolysis requires cytosolic NAD+, the authors tested whether PARP1 activation impairs glycolytic flux and whether substrates that bypass glycolysis can rescue cells after PARP1 activation. PARP1 was activated in mouse cortical astrocyte and astrocyte-neuron cocultures with the DNA alkylating agent, N-methyl- N ′-nitro- N-nitrosoguanidine (MNNG). Studies using the 2-deoxyglucose method confirmed that glycolytic flux was reduced by more than 90% in MNNG-treated cultures. The addition of 5 mmol/L of α-ketoglutarate, 5 mmol/L pyruvate, or other mitochondrial substrates to the cultures after MNNG treatment reduced cell death from approximately 70% to near basal levels, while PARP inhibitors and excess glucose had negligible effects. The mitochondrial substrates significantly reduced cell death, with delivery delayed up to 2 hours after MNNG washout. The findings suggest that impaired glycolytic flux is an important factor contributing to PARP1-mediated cell death. Delivery of alternative substrates may be a promising strategy for delayed treatment of PARP1-mediated cell death in ischemia and other disorders.
[2,4-13C2]-β-Hydroxybutyrate Metabolism in Human Brain
Authors: Pan Jullie W. , de Graaf Robin A. , Petersen Kitt F. , Shulman Gerald I. , Hetherington Hoby P. , Rothman Douglas L.
Published: November 2003

Infusions of [2,4-13C2]-β-hydroxybutyrate and 1H–13C polarization transfer spectroscopy were used in normal human subjects to detect the entry and metabolism of β-hydroxybutyrate in the brain. During the 2-hour infusion study, 13C label was detectable in the β-hydroxybutyrate resonance positions and in the amino acid pools of glutamate, glutamine, and aspartate. With a plasma concentration of 2.25 ± 0.24 mmol/L (four volunteers), the apparent tissue β-hydroxybutyrate concentration reached 0.18 ± 0.06 mmol/L during the last 20 minutes of the study. The relative fractional enrichment of 13C-4-glutamate labeling was 6.78 ± 1.71%, whereas 13C-4-glutamine was 5.68 ± 1.84%. Steady-state modeling of the 13C label distribution in glutamate and glutamine suggests that, under these conditions, the consumption of the β-hydroxybutyrate is predominantly neuronal, used at a rate of 0.032 ± 0.009 mmol · kg−1 · min−1, and accounts for 6.4 ± 1.6% of total acetyl coenzyme A oxidation. These results are consistent with minimal accumulation of cerebral ketones with rapid utilization, implying blood—brain barrier control of ketone oxidation in the nonfasted adult human brain.
Certain Forms of Matrix Metalloproteinase-9 Accumulate in the Extracellular Space after Microdialysis Probe Implantation and Middle Cerebral Artery Occlusion/Reperfusion
Authors: Planas Anna M. , Justicia Carles , Solé Sònia , Friguls Bibiana , Cervera Álvaro , Adell Albert , Chamorro Ángel
Published: November 2003

Matrix metalloproteinases (MMPs) are activated in focal cerebral ischemia. The activation of MMP-9 is involved in blood—brain barrier breakdown and tissue remodeling. The MMPs are released to the extracellular space, but the form and fate of secreted enzymes in brain are unknown. Using microdialysis in vivo, the authors studied whether ischemia-induced MMP-9 in brain tissue was related to free MMP-9 in the extracellular fluid. A microdialysis probe was placed into the right striatum and microdialysis was initiated 24 hours later in controls (n = 7). One hour prior to microdialysis, a group of rats (n = 7) was subjected to 1-hour occlusion of the right middle cerebral artery, followed by reperfusion. Dialysates were collected at discrete time points up to 24 hours, and subjected to zymography and Western blot analysis. The MMP-9 was released after ischemia and accumulated in the extracellular space at 24 hours ( P < 0.05). Free MMP-9 forms include mainly the 95-kd proform, and, to a lesser extent, dimers and cleaved active forms (70 kd), but not the 88-kd form found in tissue. Probe implantation and microdialysis increased free MMP-9 in the dialysate. This increase was concomitant with neutrophil infiltration after the mechanical lesion, as myeloperoxidase was found by means of Western blot analysis in the brain hemisphere subjected to microdialysis ( P < 0.005), and immunohistochemistry revealed the presence of myeloperoxidase stain surrounding the site of probe implantation. The results suggest that certain forms of MMP-9 are released and accumulate in the extracellular space after brain injury, and that vascular alterations and neutrophil recruitment elicit MMP-9 activation in the brain after focal ischemia and trauma.
Assessment of Acetazolamide Reactivity in Cerebral Blood Flow Using Spectral Analysis and Technetium-99m Hexamethylpropylene Amine Oxime
Authors: Takasawa Masashi , Murase Kenya , Oku Naohiko , Yoshikawa Takuya , Osaki Yasuhiro , Imaizumi Masao , Matsuzawa Hiroaki , Fujino Kouichi , Hashikawa Kazuo , Kitagawa Kazuo , Hori Masatsugu , Matsumoto Masayasu
Published: November 2003

Cerebral blood flow (CBF) can be quantified noninvasively using the brain perfusion index (BPI), determined from radionuclide angiographic data generated with technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO). Previously, the BPI has been calculated using graphical analysis (GA); however, the GA method is greatly affected by the first-pass extraction fraction and retention fraction, which are not only variable, but lower in cases with an increased CBF, such as after the administration of acetazolamide. Thus, GA-calculated BPI values (BPIG) may not reflect the absolute CBF. The objective of this study was to use the spectral analysis of radionuclide angiographic data collected using 99mTc-HMPAO to examine changes in the BPI after the administration of acetazolamide. We studied the CBF of both cerebral hemispheres in six healthy male volunteers; the BPI was measured at rest and after the intravenous administration of 1 g of acetazolamide. In all participants, an H215O positron emission tomography (PET) examination was also performed, and the spectral analysis—calculated BPI values (BPIS) and BPIG values were compared with the actual CBF measured using H215O PET (mCBFPET). The BPIS was 1.070 ± 0.051 (mean ± SD) at rest and 1.497 ± 0.098 after acetazolamide; the corresponding BPIG values were 0.646 ± 0.073 and 0.721 ± 0.107. The BPIS values were significantly correlated with the mCBFPET values, whereas the BPIG values were not. According to the BPIS values, the increase in BPI after the intravenous administration of acetazolamide was 40.1 ± 8.4%, as opposed to an increase of only 11.3 ± 6.5% according to the BPIG values. These results suggest that the spectral analysis of 99mTc-HMPAO—generated data yields a more reliable BPI than GA for the quantification of CBF after acetazolamide administration.
Expression of Brain-Specific Angiogenesis Inhibitor 2 (BAI2) in Normal and Ischemic Brain: Involvement of BAI2 in the Ischemia-Induced Brain Angiogenesis
Authors: Kee Hae Jin , Koh Jeong Tae , Kim Mi-Young , Ahn Kyu Youn , Kim Jong Keun , Bae Choon Sang , Park Sung Sik , Kim Kyung Keun
Published: November 2003

Previously, the authors cloned and characterized murine brain-specific angiogenesis inhibitor 1 (mBAI1). In this study, the authors cloned mBAI2 and analyzed its functional characteristics. Northern and Western blot analyses demonstrated a unique developmental expression pattern of mBAI2 in the brain. The expression level of mBAI2 appeared to increase as the development of the brain progressed. Reverse transcription-polymerase chain reaction (RT-PCR) analyses demonstrated the existence of alternative splice variants of mBAI2, which were defective in parts of type I repeat of thrombospondin or the third cytoplasmic loop of the seven-span transmembrane domain that were considered essential to the functions of mBAI2. The expressions of spliced variants in the brain were differently regulated compared with wild-type mBAI2 during development and ischemic conditions. In situ hybridization analyses of the brain showed the same localization of BAI2 as BAI1, such as in most neurons of cerebral cortex. In the in vivo focal cerebral ischemia model and the in vitro hypoxic cell culture model with cobalt, BAI2 expression decreased after hypoxia and preceded the increased expression of vascular endothelial growth factor (VEGF). RT-PCR analysis of antisense BAI2 cDNA-transfected SHSY5Y cells showed an increased VEGF expression as well as a decreased BAI2 expression. Immunohistochemical study of focal ischemic cortex showed that the regional localization of decreased BAI2 was related to the formation of new vessels. These results suggest that the brain-specific developmental expression pattern of angiostatic BAI2 is correlated with the decreased neovascularization in the adult brain, and that angiostatic BAI2 participates in the ischemia-induced brain angiogenesis in concert with angiogenic VEGF.
Transforming Growth Factor-β1—Modulated Cerebral Gene Expression
Authors: Lesné Sylvain , Blanchet Sophie , Docagne Fabian , Liot Géraldine , Plawinski Laurent , MacKenzie Eric T. , Auffray Charles , Buisson Alain , Piétu Geneviève , Vivien Denis
Published: November 2003

Transforming growth factor-β1 (TGF-β1) plays a central role in the response of the brain to different types of injury. Increased TGF-β1 has been found in the central nervous system of patients with acute or chronic disorders such as stroke or Alzheimer disease. To further define the molecular targets of TGF-β1 in cerebral tissues, a selection of high-density cDNA arrays was used to characterize the mRNA expression profile of 7,000 genes in transgenic mice overexpressing TGF-β1 from astrocytes as compared with the wild-type line. Selected findings were further evaluated by reverse transcription-polymerase chain reactions from independent transgenic and wild-type mice. Furthermore, the expression pattern of seven selected genes such as Delta-1, CRADD, PRSC-1, PAI-1, Apo-1/Fas, CTS-B, and TβR-II were confirmed in either cultured cortical neurons or astrocytes following TGF-β1 treatment. The authors' observations enlarge the repertoire of known TGF-β1–modulated genes and their possible involvement in neurodegenerative processes.
Current Management of Purpura Fulminans: A Multicenter Study
Authors: Warner P. M. , Kagan R. J. , Yakuboff K. P. , Kemalyan N. , Palmieri T. L. , Greenhalgh D. G. , Sheridan R. L. , Mozingo D. W. , Heimbach D. M. , Gibran N. S. , Engrav L. , Saffle J. R. , Edelman L. S. , Warden G. D.
Published: November 2003

Seven burn centers performed a 10-yr retrospective chart review of patients diagnosed with purpura fulminans. Patient demographics, etiology, presentation, medical and surgical treatment, and outcome were reviewed. A total of 70 patients were identified. Mean patient age was 13 yr. Neisseria meningitidis was the most common etiologic agent in infants and adolescents whereas Streptococcus commonly afflicted the adult population. Acute management consisted of antibiotic administration, volume resuscitation, ventilatory and inotropic support, with occasional use of corticosteroids (38%) and protein C replacement (9%). Full-thickness skin and soft-tissue necrosis was extensive, requiring skin grafting and amputations in 90% of the patients. One fourth of the patients required amputations of all extremities. Fasciotomies when performed early appeared to limit the level of amputation in 6 of 14 patients. Therefore, fasciotomies during the initial management of these patients may reduce the depth of soft-tissue involvement and the extent of amputations.
Pain Control in a Randomized, Controlled, Clinical Trial Comparing Moist Exposed Burn Ointment and Conventional Methods in Patients With Partial-Thickness Burns
Authors: Ang Erik , Lee S.-T. , Gan Christine S.-G. , Chan Y.-H. , Cheung Y.-B. , Machin D.
Published: November 2003

Conventional management of partial-thickness burn wounds includes the use of paraffin gauze dressing, frequently with topical silver-based antibacterial creams. Some creams form an overlying slough that renders wound assessment difficult and are painful upon application. An alternative to conventional management, moist exposed burn ointment (MEBO), has been proposed as a topical agent that may accelerate wound healing and have antibacterial and analgesic properties. One hundred fifteen patients with partial-thickness burns were randomly assigned to conventional (n = 58) or MEBO treatment (n = 57). A verbal numerical rating score of pain was made in the morning, after burn dressing, and some 8 hours later. Patient pain profiles were summarized by locally weighted regression smoothing technique curves and the difference between treatments estimated using multilevel regression techniques. Mean verbal numerical rating scale pain levels (cm) in week 1 for all patients were highest at 3.2 for the after dressing assessment, lowest in the evening at 2.6, and intermediate in the morning at 3.0. This pattern continued at similar levels in week 2 and then declined by a mean of 0.5 in all groups in week 3. There was little evidence to suggest a difference in pain levels by treatment group with the exception of the postdressing pain levels in the first week when those receiving MEBO had a mean level of 0.7 cm (95% confidence interval, 0.2 to 1.1) lower than those on conventional therapy. MEBO appeared to bring greater pain relief for the postdressing assessment during the first week after burns. This initial relief, together with comparable pain levels experienced on other occasions, indicates that MEBO could be an alternative to conventional burns management.
Comparison of Surface Swab Cultures and Quantitative Tissue Biopsy Cultures to Predict Sepsis in Burn Patients: A Prospective Study
Authors: Sjöberg T. , Mzezewa S. , Jönsson K. , Robertson V. , Salemark L.
Published: November 2003

This study aimed at evaluating the possibility of predicting septicemia in burn patients by using wound surface and tissue culture techniques as well as blood cultures. Fifty patients with full-thickness burn wounds covering at least 10% of the total body surface area were included. Signs of septicemia were noted in 21 patients (42%) and 29 patients died (58%). The bacterial colonization of the burn wounds consisted mainly of Staphylococcus aureus and Pseudomonas aeruginosa. Sepsis was better correlated to quantitative burn tissue biopsy cultures than surface swab cultures but the time needed for processing limits its predictive and therapeutic value.