bluuebunny/crossref_metadata_2025 huggingface dataset:
Overexpression of the Cell Death Suppressor Bcl-w in Ischemic Brain: Implications for a Neuroprotective Role via the Mitochondrial Pathway
Authors: Yan Chaohua , Chen Jun , Chen Dexi , Minami Manabu , Pei Wei , Yin Xiao-Ming , Simon Roger P.
Published: November 2003

Bcl-w is a newly described cell death suppressor member of the Bcl-2 gene family. As these genes may have a role in the outcome of ischemic brain injury, the regional expression of Bcl-w protein in rat brain was examined at 6 to 72 hours after 90 minutes of transient middle cerebral artery occlusion. Bcl-w protein, although constitutively expressed at low levels in nonischemic brain, was found to be overexpressed in ischemic brain at all time points studied. Up-regulation of Bcl-w protein was particularly abundant in the penumbral region of the cortex and mainly in cells lacking DNA fragmentation. In the cortical penumbra, Bcl-w protein was detected predominantly in neurons and showed mitochondrial localization, as determined using double-label immunohistochemistry. Bcl-w expression was also detectable, to a lesser extent, in reactive astrocytes in the infarct border zone and in microvessel walls in the infarct regions. At the mechanistic level, incubation of isolated brain mitochondria with the addition of recombinant Bax or high concentration of calcium resulted in release of cytochrome c from the mitochondria. In the presence of recombinant Bcl-w protein, however, the release of cytochrome c induced by Bax or calcium was largely inhibited. Further, recombinant Bcl-w protein inhibited calcium-induced loss of mitochondrial transmembrane potential, indicative of permeability transition, in a dose-dependent manner. These results suggest that Bcl-w may be an endogenous neuroprotectant against ischemic neuronal death and that, like its analogues such as Bcl-2 and Bcl-x-long, Bcl-w may achieve this protection via the mitochondrial death-regulatory pathway.
Analysis of Four Dopaminergic Tracers Kinetics Using Two Different Tissue Input Function Methods
Authors: Sossi V. , Holden J. E. , Chan G. , Krzywinski M. , Stoessl A. J. , Ruth T. J.
Published: November 2003

The integrity of the dopaminergic system can be studied using positron emission tomography. The presynaptic tracers [11C]-methylphenidate and [11C]dihydrotetrabenazine (DTBZ) are used to investigate the dopamine transporter availability, the dopamine vesicular transporter integrity; the post-synaptic tracers [11C]-raclopride and [11C]-Schering 23990 (SCH) are used to probe the D2 and D1 receptors. These are reversible tracers, where the binding potential (BP) = Bmax/Kd often is used to quantify the amount of their specific binding to the sites of interest. The simplified tissue input methods to calculate BP are attractive, since they do not require a blood input function. The suitability and performance of two such methods were evaluated: the Logan graphical tissue method, and the Lammertsma reference tissue method (RTM). The BP estimates obtained with the two methods were nearly identical in most cases, with similar reliability and reproducibility indicating that all four tracers satisfy the assumptions required by each method. The correlations among the fitted parameters obtained from the RTM were estimated and were found not to introduce noticeable bias in the RTM BP and R1 estimates. R1 showed low intersubject and intrasubject variability. The k2 estimate showed good reliability for SCH with cerebellar input function and DTBZ with occipital input function.
Immunohistochemical Detection of Leukemia Inhibitory Factor After Focal Cerebral Ischemia in Rats
Authors: Suzuki Shigeaki , Tanaka Kortaro , Nogawa Shigeru , Ito Daisuke , Dembo Tomohisa , Kosakai Arifumi , Fukuuchi Yasuo
Published: November 2003

The cytokine leukemia inhibitory factor (LIF) modulates neuronal function during development and promotes neuronal survival after peripheral nerve injury, but little is known about LIF expression after cerebral ischemia. In the present study, the localization of LIF protein was immunohistochemically examined in rats after 3.5, 12, 24, 48, and 96 hours of reperfusion following 1.5 hours of middle cerebral artery occlusion (MCAO) induced by the intraluminal suture method. Double-staining immunohistochemistry with microtubule-associated protein-2 (MAP2), glial fibrillary acidic protein (GFAP), lectin histochemistry, and interleukin (IL) 6 was also performed. The sham group and immunosorption test did not show any clear LIF immunoreactivity. Definite LIF immunoreactivity was first detected after 12 hours of reperfusion in each of the brain regions examined: ischemic core, periinfarct region, and contralateral cortex. However, expression of LIF was most prominent in the periinfarct region at each time point, peaked at 24 hours, and then gradually declined until 96 hours of reperfusion. Some LIF-positive neurons in the periinfarct region expressed IL-6. At 96 hours of reperfusion, GFAP-labeled astrocytes around the infarct core also expressed LIF protein. Induction of LIF mRNA and protein was also confirmed by reverse transcription polymerase chain reaction and western blot analysis, respectively. These findings suggest that LIF expression in ischemically threatened neurons may reflect a repair or defense mechanism against the ischemic insult.
Expression of Fas and Fas Ligand After Experimental Traumatic Brain Injury in the Rat
Authors: Beer Ronny , Gerhard Franz , Schöpf Marion , Reindl Markus , Zelger Bernhard , Schmutzhard Erich , Poewe Werner , Kampfl Andreas
Published: November 2003

Apoptotic cell death plays an important role in the cascade of neuronal degeneration after traumatic brain injury (TBI), but the underlying mechanisms are not fully understood. However, increasing evidence suggests that expression of Fas and its ligand (FasL) could play a major role in mediating apoptotic cell death in acute and chronic neurologic disorders. To further investigate the temporal pattern of Fas and FasL expression after experimental TBI in the rat, male Sprague Dawley rats were subjected to unilateral cortical impact injury. The animals were killed and examined for Fas and FasL protein expression and for immunohistologic analysis at intervals from 15 minutes to 14 days after injury. Increased Fas and FasL immunoreactivity was seen in the cortex ipsilateral to the injury site from 15 minutes to 72 hours after the trauma, respectively. Immunohistologic investigation demonstrated a differential pattern of Fas and FasL expression in the cortex, respectively: increased Fas immunoreactivity was seen in cortical astrocytes and neurons from 15 minutes to 72 hours after the injury. In contrast, increased expression of FasL was seen in cortical neurons, astrocytes, and microglia from 15 minutes to 72 hours after impact injury. Concurrent double-labeling examinations using terminal deoxynucleotidyl tranferase-mediated deoxyuridine-biotin nick end labeling identified Fas- and FasL-immunopostive cells with high frequency in the cortex ipsilateral to the injury site. In contrast, there was no evidence of Fas- and FasL-immunopositive cells in the hippocampus ipsilateral to the injury site up to 14 days after the trauma. Further, Fas and FasL immunoreactivity was absent in the contralateral cortex and hippocampus at all time points investigated. These results reveal induction of Fas and FasL expression in the cortex after TBI in the rat. Further, these data implicate an involvement of Fas and FasL in the pathophysiologic mechanism of apoptotic neurodegeneration after TBI. Last, these data suggest that strategies aimed to repress posttraumatic Fas- and FasL-induced apoptosis may open new perspectives for the treatment of TBI.
Preganglionic and Postganglionic Neurons Responsible for Cerebral Vasodilation Mediated by Nitric Oxide in Anesthetized Dogs
Authors: Toda Noboru , Ayajiki Kazuhide , Tanaka Toshiki , Okamura Tomio
Published: November 2003

The authors performed investigations to functionally determine the route of efferent innervation in vivo responsible for cerebral vasodilation mediated by nitric oxide (NO). In anesthetized beagles, electrical stimulation of the pterygopalatine ganglion vasodilated ipsilateral cerebral arteries such as the middle cerebral and posterior communicating arteries. Intravenous injections of NG-nitro-L-arginine (L-NA) markedly inhibited the response to nerve stimulation, and the effect was reversed by L-arginine. Stimulation of the proximal portion of the greater superficial petrosal nerve, upstream of the pterygopalatine ganglion, also produced cerebral vasodilation, which was abolished by L-NA and restored by L-arginine. Treatment with hexamethonium abolished the response to stimulation of the petrosal nerve but did not affect the response to pterygopalatine ganglion stimulation. Destruction of the pterygopalatine ganglion by cauterization constricted the cerebral arteries. Postganglionic denervation abolished the vasodilation, lacrimation, and nasal secretion induced on the ipsilateral side by stimulation of the pterygopalatine ganglion and petrosal nerve. The vasodilator response was suppressed by L-NA but unaffected by atropine, whereas lacrimation and nasal secretion were abolished solely by atropine. It is concluded that postganglionic neurons from the pterygopalatine ganglion play crucial roles in cerebral vasodilation mediated by NO from the nerve, and preganglionic neurons, possibly from the superior salivatory nucleus through the greater superficial petrosal nerve, innervate the pterygopalatine ganglion. Tonic discharges from the vasomotor center participate significantly in the maintenance of cerebral vasodilation.
Effects of Graded Hyperventilation on Cerebral Blood Flow Autoregulation in Experimental Subarachnoid Hemorrhage
Authors: Ma XiaoDong , Willumsen Lisette , Hauerberg John , Pedersen Daniella Bach , Juhler Marianne
Published: November 2003

An impaired CBF autoregulation can be restored by hyperventilation at a PaCO2 level of about 2.9 to 4.1 kPa (22 to 31 mm Hg). However, it is uncertain whether the restoring effect can take place at lesser degrees of hypocapnia. In the current study, CBF autoregulation was studied at four PaCO2 levels: 5.33 kPa (40 mm Hg, normoventilation), 4.67 kPa (35 mm Hg, slight hyperventilation), 4.00 kPa (30 mm Hg, moderate hyperventilation), and 3.33 kPa (25 mm Hg, profound hyperventilation). At each PaCO2 level, eight rats 2 days after experimental subarachnoid hemorrhage (SAH) and eight shamoperated controls were studied. The CBF was measured by the intracarotid 133Xe method. The CBF autoregulation was found to be intact in all controls but completely disturbed in the normoventilated SAH rats. However, by slight hyperventilation, CBF autoregulation was restored in seven of eight SAH rats with a decline in CBF of 10%. The CBF autoregulation was found intact in all of the moderately or profoundly hyperventilated SAH rats, whereas the decline in CBF was 21% and 28%, respectively. In conclusion, hyperventilation to a PaCO2 level between 4.00 and 4.67 kPa (30 to 35 mm Hg) appears to be sufficient for reestablishing an impaired autoregulation after SAH.
Temporal Changes of the Apparent Diffusion Coefficients of Water and Metabolites in Rats With Hemispheric Infarction: Experimental Study of Transhemispheric Diaschisis in the Contralateral Hemisphere at 7 Tesla
Authors: Abe Osamu , Okubo Toshiyuki , Hayashi Naoto , Saito Nobuhito , Iriguchi Norio , Shirouzu Ichiro , Kojima Yoshiki , Masumoto Tomohiko , Ohtomo Kuni , Sasaki Yasuhito
Published: November 2003

The purpose of the present study was to clarify the temporal changes of the apparent diffusion coefficients (ADCs) of cerebral metabolites during early focal ischemia using stimulated echo acquisition mode with short echo time at a 7 T magnet to assess the pathophysiology of the reduction in diffusion properties observed both in the ischemic cerebral hemisphere and in the contralateral hemisphere. The ADCs of metabolites in the infarcted hemisphere 1 hour and 3 hours after the onset of ischemia decreased with 25% and 29% for choline-containing compounds (Cho), 16% and 26% for creatine and phosphocreatine (Cre), and 19% and 19% for N-acetylaspartate (NAA), respectively, compared with the ADC values 2 hours later in the contralateral hemisphere. There were decreases in the ADC of Cho, Cre, and NAA with 21%, 7%, and 18% 8 hours later, respectively, in the noninfarcted hemisphere, which suggested transhemispheric diaschisis in rats with focal cerebral ischemia. The present study proposed that the diffusion characteristics of the brain metabolites might offer new insights into circulatory and metabolic alteration in the cerebral intracellular circumstance.
Model of Blood–Brain Transfer of Oxygen Explains Nonlinear Flow-Metabolism Coupling During Stimulation of Visual Cortex
Authors: Vafaee Manouchehr S. , Gjedde Albert
Published: November 2003

The coupling between cerebral metabolic rate of oxygen (CMRO2) and blood flow (CBF) in response to visual stimulation was evaluated by means of a model of oxygen delivery. The model predicted a nonlinear relationship between stimulus-evoked changes of oxygen consumption and blood flow. The magnitude of the CMRO2/CBF ratio index ( IO2) was used to indicate the degree of flow-metabolism coupling prevailing in specific areas of the brain during physiological stimulation. Therefore, the index provided a measure of the blood oxygenation level dependent (BOLD) magnetic resonance contrast. To evaluate the changes of IO2 in response to visual stimulation, the model was applied to the effect of a changing flicker rate of a visual stimulus on the magnitudes of CBF, CMRO2, and oxygen diffusion capacity, in the human brain. Positron emission tomography (PET) was used to measure the CBF and the CMRO2 in 12 healthy volunteers who viewed a cross-hair (baseline) or a yellow-blue annular checkerboard reversing at frequencies of 1, 4, or 8 Hz. The magnitude of CBF in the primary visual cortex increased as a function of the checkerboard reversal rate and reached a maximum at the frequency of 8 Hz ( z = 16.0), while the magnitude of CMRO2 reached a maximum at 4 Hz ( z = 4.0). Therefore, the calculated IO2 was lower at 8 Hz than at 1 and 4 Hz, in contrast to the oxidative metabolic rate that reached its maximum at 4 Hz. The model explained the increase of oxygen consumption as the combined effect of increased blood flow and increased oxygen diffusion capacity in the region of visual activation.
Early N-Acetylaspartate Depletion Is a Marker of Neuronal Dysfunction in Rats and Primates Chronically Treated with the Mitochondrial Toxin 3-Nitropropionic Acid
Authors: Dautry Caroline , Vaufrey Françoise , Brouillet Emmanuel , Bizat Nicolas , Henry Pierre-Gilles , Condé Françoise , Bloch Gilles , Hantraye Philippe
Published: November 2003

N-acetylaspartate (NAA) quantification by 1H-magnetic resonance spectroscopy has been commonly used to assess in vivo neuronal loss in neurodegenerative disorders. Here, the authors used ex vivo and in vivo1H-magnetic resonance spectroscopy in rat and primate models of progressive striatal degeneration induced by the mitochondrial toxin 3-nitropropionate (3NP) to determine whether early NAA depletions could also be associated with neuronal dysfunction. In rats that were treated for 3 days with 3NP and had motor symptoms, the authors found a significant decrease in NAA concentrations, specifically restricted to the striatum. No cell loss or dying cells were found at this stage in these animals. After 5 days of 3NP treatment, a further decrease in striatal NAA concentrations was observed in association with the occurrence of dying neurons in the dorsolateral striatum. In 3NP-treated primates, a similar striatal-selective and early decrease in NAA concentrations was observed after only a few weeks of neurotoxic treatment, without any sign of ongoing cell death. This early decrease in striatal NAA was partially reversed after 4 weeks of 3NP withdrawal. These results demonstrate that early NAA depletions reflect a reversible state of neuronal dysfunction preceding cell degeneration and suggest that in vivo quantification of NAA 1H-magnetic resonance spectroscopy may become a valuable tool for assessing early neuronal dysfunction and the effects of potential neuroprotective therapies in neurodegenerative disorders.
Induced Hypothermia in Experimental Pneumococcal Meningitis
Authors: Angstwurm Klemens , Reuß Stefanie , Freyer Dorette , Arnold Guy , Dirnagl Ulrich , Schumann Ralf R. , Weber Joerg R.
Published: November 2003

Pneumococcal meningitis resulting from Streptococcus pneumoniae has a death rate of 28% in adults. In severe head injury and stroke, inflammatory changes and intracranial hypertension are improved by induced hypothermia, which also is neuroprotective. We hypothesized that moderate hypothermia ameliorates inflammatory changes in experimental pneumococcal meningitis. Wistar rats were cooled systemically, and meningitis was induced by pneumococcal cell wall components. The increase of regional cerebral blood flow in the meningitis animals was blocked by hypothermia at 6 hours. The reduction of intracranial pressure correlated with temperature. The influx of leukocytes into the cerebrospinal fluid and levels of tumor necrosis factor α in the cerebrospinal fluid were decreased. Cooling the animals 2 hours after meningitis induction to 30.5°C was also protective. We conclude that hypothermia is a new adjuvant approach to reduce meningitis-induced changes, in particular intracranial pressure, in the early phase of the disease.
Modeling Dynamic PET-SPECT Studies in the Wavelet Domain
Authors: Turkheimer Federico E. , Banati Richard B. , Visvikis Dimitris , Aston John A. D. , Gunn Roger N. , Cunningham Vincent J.
Published: November 2003

This work develops a theoretical framework and corresponding algorithms for the modeling of dynamic PET-SPECT studies both in time and space.

The problem of estimating the spatial dimension is solved by applying the wavelet transform to each scan of the dynamic sequence and then performing the kinetic modeling and statistical analysis in the wavelet domain. On reconstruction through the inverse wavelet transform, one obtains parametric images that are consistent estimates of the spatial patterns of the kinetic parameter of interest.

The theoretical setup allows the use of linear techniques currently used in PET-SPECT for kinetic analysis. The method is applied to artificial and real data sets. The application to dynamic PET-SPECT studies was performed both for validation purposes, when the spatial patterns are known, and for illustration of the advantages offered by the technique in case of tracers with an unknown pattern of distribution.
Investigation of Estrogen Status and Increased Stroke Sensitivity on Cerebral Blood Flow after a Focal Ischemic Insult
Authors: Carswell Hilary V. O. , Anderson Niall H. , Morton James J. , McCulloch James , Dominiczak Anna F. , Macrae I. Mhairi
Published: November 2003

Recently the authors have shown that female stroke-prone spontaneously hypertensive rats (SHRSPs) in proestrus (high endogenous estrogen), sustain more than 20% smaller infarcts after middle cerebral artery occlusion (MCAO) compared with SHRSPs in metestrus (low endogenous estrogen). Because estrogen has vasodilator properties, the authors investigated whether the estrous state influences cerebral blood flow (CBF) after MCAO. CBF was measured 2.5 hours after a distal MCAO by [14C]iodo-antipyrine autoradiography in conscious SHRSPs either in metestrus or in proestrus. There were no significant differences in CBF when analyzed either at predetermined anatomic regions or by cumulative distribution analysis of areas with flow <25 mL/100 g/min. As a positive internal control, the authors compared results in SHRSPs with those in their normotensive reference strain, Wistar Kyoto rat. SHRSPs displayed more severe and widespread ischemia than Wistar Kyoto rats. Thus, the absence of demonstrable CBF differences between estrous states appears to be unrelated to the CBF measurement paradigm. In conclusion, the smaller infarct size afforded in proestrus in SHRSPs is unlikely to be due to an influence on CBF.
Leukocyte-Endothelium Interactions in Pial Venules during the Early and Late Reperfusion Period after Global Cerebral Ischemia in Gerbils
Authors: Uhl Eberhard , Beck Jürgen , Stummer Walter , Lehmberg Jens , Baethmann Alexander
Published: November 2003

The contribution of leukocytes to secondary brain damage after cerebral ischemia is still under discussion. The purpose of the present study was to examine the pial microcirculation after global cerebral ischemia while focusing on leukocyte–endothelium interactions during the early and late reperfusion period of up to 4 days. A closed cranial window technique that leaves the dura mater intact was used. Global cerebral ischemia of 15 minutes' duration was induced in male Mongolian gerbils (n = 91). Pial microcirculation was observed by intravital fluorescence microscopy. Leukocyte–endothelium interactions (LEIs) in pial venules, vessel diameters, capillary density, and regional microvascular blood flow measured by laser Doppler flowmetry were quantified during 3 hours of reperfusion and in intervals up to 4 days after ischemia. Within 3 hours of reperfusion, the number of leukocytes (cells/100 μm × minute) rolling along or adhering to the venular endothelium increased from 0.1 ± 0.2 to 28.4 ± 17.4 ( P < 0.01 vs. control) and from 0.2 ± 0.2 to 4.0 ± 3.8 ( P < 0.05), respectively. There was no capillary plugging by leukocytes; capillary density remained unchanged. In the late reperfusion period, at 7 hours after ischemia, LEIs had returned to baseline values. Furthermore, from 12 hours to 4 days after ischemia, no LEIs were observed. Changes in regional microvascular blood flow did not correlate with LEIs. Global cerebral ischemia of 15 minutes' duration induces transient LEIs that reach a maximum within 3 hours of reperfusion and return to baseline at 7 hours after ischemia. LEIs are not related to changes in microvascular perfusion, which suggests mainly that the expression of adhesion receptors is necessary to induce LEIs rather than rheologic factors. It seems unlikely that this short-lasting activation of leukocytes can play a role in the development of secondary brain damage.
Suppression of Endogenous bcl-2 Expression by Antisense Treatment Exacerbates Ischemic Neuronal Death
Authors: Chen Jun , Simon Roger P. , Nagayama Tesuya , Zhu Raymond , Loeffert J. Eric , Watkins Simon C. , Graham Steven H.
Published: November 2003

Previous studies have shown that overexpression of bcl-2 in transgenic mice or by viral vectors protects the brain against cerebral ischemia. However, it is not known whether bcl-2, which is endogenously expressed in response to ischemia, exerts a protective effect. To address this question, the authors blocked the endogenous expression of bcl-2 after ischemia using antisense oligodeoxynucleotides (ODN). Antisense, sense, scrambled ODN, or vehicles were infused in the lateral ventricle of the rat for 24 hours after 30 minutes of temporary middle cerebral artery occlusion. Twenty-four hours later the brains were removed and bcl-2 protein expression was assayed by Western blot. Antisense ODN, but not sense or scrambled ODN treatment, significantly inhibited bcl-2 protein expression after ischemia. Bcl-2 protein expression was also studied 24 hours after 60 minutes of temporary middle cerebral artery occlusion in vehicle and antisense ODN-treated rats. After 60 minutes of ischemia and vehicle treatment, bcl-2 was expressed in many neurons in the ventral cortical mantle and the medial striatum. After antisense ODN treatment there were few neurons in this region expressing bcl-2, instead most neurons TUNEL labeled. Treatment with the antisense ODN, but not sense ODN, increased infarction volume as determined by cresyl violet staining 72 hours after ischemia compared with vehicle controls. These results suggested that endogenously expressed bcl-2 promoted survival in ischemic neurons and was not simply an epiphenomenon in neurons already destined to live or die.
Parallel Gene Expression Monitoring using Oligonucleotide Probe Arrays of Multiple Transcripts with an Animal Model of Focal Ischemia
Authors: Soriano Marc A. , Tessier Michel , Certa Ulrich , Gill Ramanjit
Published: November 2003

High density oligonucleotide arrays offer tremendous potential to study gene changes occurring in disease states. The authors described the first case of using a custom designed high density oligonucleotide probe array containing 750 genes to monitor the changes in mRNA transcript levels occurring after focal ischemia for a period of 3 hours. Permanent middle cerebral artery occlusion in the rat resulted in neuronal degeneration in the dorsolateral cortex and striatum over a time course of 24 hours. Comparing the changes in hybridization levels in the frontal and parietal cortices and the striatum, between the ipsilateral and contralateral sides of the brain using the probe arrays resulted in the up-regulation of 24 genes, which showed greater than a twofold change. Very few genes were found to be downregulated after the ischemic insult. Many of the immediate early genes (IEGs) such as c-fos, NGFI-A, NGFI-C, and Krox-20 were found to be robustly up-regulated in the three different regions studied. Other genes that were up-regulated in perifocal regions included Arc, Inhibin-β-A, and the phosphatases MKP-1 and MKP-3. The hybridization signal intensity from the probe arrays enabled quantification of many genes relative to one another, and robust changes in expression were obtained with very little interanimal variability. Furthermore, the authors were able to validate the increased expression of NGFI-C and Arc using in situ hybridization. This represented the first example of using high density oligonucleotide probe arrays in studying the expression of many genes in parallel and in discrete brain regions after focal ischemia.
Alteration of MAP Kinase Pathways after Transient Forebrain Ischemia
Authors: Hu Bing R. , Liu Chun L. , Park Darren J.
Published: November 2003

Extracellular regulated kinase (ERK) transduce growth factor signals while c-Jun NH(2)-terminal kinase (JNK) delivers stress signals into the nuclei for regulation of gene expression. These signaling pathways were studied by laser-scanning confocal microcopy and Western blot analysis using phospho-specific antibodies on rat brains that were subjected to 15 minutes transient forebrain ischemia followed by varied periods of reperfusion. Extracellular regulated kinase was activated at 30 minutes and 4 hours of reperfusion in the nuclei and dendrites of surviving dentate gyrus (DG) cells, but not in dying CA1 neurons after ischemia. Tyrosine phosphorylation of Trk kinase, an ERK upstream growth factor receptor, was elevated in the DG tissue, and to a lesser extent in the CA1 region. In addition, phosphorylation of activating transcription factor-2 (ATF-2) and c-Jun was selectively increased in CA1 dying neurons during the late period of reperfusion. These findings suggested that the Trk-ERK signaling pathway might be neuroprotective for dentate granule cells. The activation of ATF-2 and c-Jun pathways in the late period of reperfusion in CA1 dying neurons might reflect damage signals in these neurons. These results suggested that the lack of protective signals acting in concert with the presence of damage signals in CA1 neurons after ischemia might contribute to delayed neuronal death after transient forebrain ischemia.
Saccadic Suppression Induces Focal Hypooxygenation in the Occipital Cortex
Authors: Wenzel Rüdiger , Wobst Petra , Heekeren Hauke H. , Kwong Kenneth K. , Brandt Stephan A. , Kohl Matthias , Obrig Hellmuth , Dirnagl Ulrich , Villringer Arno
Published: November 2003

This study investigated how a decrease in neuronal activity affects cerebral blood oxygenation employing a paradigm of acoustically triggered saccades in complete darkness. Known from behavioral evidence as saccadic suppression, electrophysiologically it has been shown in monkeys that during saccades an attenuation of activity occurs in visual cortex neurons ( Duffy and Burchfiel, 1975 ). In study A, using blood oxygen level-dependent (BOLD) contrast functional magnetic resonance imaging (fMRI), the authors observed signal intensity decreases bilaterally at the occipital pole during the performance of saccades at 2 Hz. In study B.1, the authors directly measured changes in deoxyhemoglobin [deoxy-Hb] and oxyhemoglobin [oxy-Hb] concentration in the occipital cortex with near-infrared spectroscopy (NIRS). Whereas a rise in [deoxy-Hb] during the performance of saccades occurred, there was a drop in [oxy-Hb]. In a second NIRS study (B.2), subjects performed saccades at different rates (1.6, 2.0, and 2.3 Hz). Here the authors found the increase in deoxy-Hb and the decrease of oxy-Hb to be dependent on the frequency of the saccades. In summary, the authors observed a focal hypooxygenation in the human visual cortex dependent on the saccade-frequency in an acoustically triggered saccades paradigm. This could be interpreted as evidence that corresponding to the focal hyperoxygenation observed in functional brain activation, caused by an excessive increase in cerebral blood flow (CBF) over the increase in CMRO2 during decreased neuronal activity CBF, is more reduced than oxygen delivery.
Striatal Kinetic Modeling of FDOPA with a Cerebellar-Derived Constraint on the Distribution Volume of 3OMFD: A PET Investigation using Non-Human Primates
Authors: Shoghi-Jadid Kooresh , Huang Sung-Cheng , Stout David B. , Yee Randa E. , Yeh Eric L. , Farahani Keyvan F. , Satyamurthy Nagichettiar , Phelps Michael E. , Barrio Jorge R.
Published: November 2003

The peripherally born metabolite of FDOPA, 3-O-Methyl-FDOPA (3OMFD), crosses the blood-brain barrier, thus complicating positron emission tomography-FDOPA (PET-FDOPA) data analysis. In previous reports the distribution volume (DV) of 3OMFD was constrained to unity. We have recently shown that the forward transport rate-constant of FDOPA ( KS1) and the cerebellum-to-plasma ratio ( Cb/ Cp), a measure for the DV of 3OMFD, are functions of plasma large neutral amino acid (LNAA) concentration. Given large interstudy and intersubject differences in plasma LNAA levels, variations in the DV of 3OMFD are significant. In this report, the authors propose a constraint on the DV of 3OMFD that accounts for these variations. Dynamic PET-FDOPA scans were performed on 12 squirrel monkeys and 12 vervet monkeys. Two sets of constraints were employed on the compartmental model—M1 or M2. In M1, the striatal DV of 3OMFD was constrained to unity; in M2, the striatal DV of 3OMFD was constrained to an estimate derived from the cerebellum. Striatal and cerebellar time-activity curves were fitted using FDOPA and 3OMFD plasma input functions. The estimate of KS1 and that of the compartmental FDOPA uptake-constant ( Ki), both obtained using M2, were adjusted to values corresponding to average LNAA levels. Finally, Ki was compared with the graphical uptake-constant ( PKi). With the use of constraint M2, intersubject variability of squirrel monkey kS3 and Ki was reduced by 45% and 53%, respectively; and for vervet monkeys, by 54% and 44%, respectively. Intersubject variability of Kl and Ki was further reduced after correction for variations in intersubject plasma LNAA levels (for squirrel monkeys, by 67% and 41%; for vervet monkeys, by 40% and 36%, respectively). Ki correlation to PKi was enhanced to identity. Finally, average cerebellar kC2 estimates were more than 2.5-fold higher than striatal kS2 estimates ( P < 0.0001). In modeling of PET-FDOPA data, it cannot be assumed that the DV of 3OMFD is unity. The cerebellar-derived constraint furnishes a reliable estimate for the DV of 3OMFD. Invoking the constraint and correcting for variations in plasma LNAA significantly reduced interstudy and intersubject variations in parameter estimates.
Altered Central Nervous System Cytokine-Growth Factor Expression Profiles and Angiogenesis in Metallothionein-I+II Deficient Mice
Authors: Penkowa Milena , Carrasco Javier , Giralt Mercedes , Molinero Amalia , Hernández Joaquín , Campbell Iain L. , Hidalgo Juan
Published: November 2003

To study the importance of metallothionein-I and -II (MT-I+II) for brain inflammation and regeneration, the authors examined normal and MT-I+II knock-out (MT-KO) mice subjected to a cortical freeze injury. Normal mice showed profound neurodegeneration, inflammation, and gliosis around the injury, which was repaired by 20 days postlesion (dpl). However, in MT-KO mice the lesion-associated inflammation was still present as late as 90 dpl. Scanning electron microscopy demonstrated that the number of capillaries was lower, and ultrastructural preservation of the lesioned parenchyma was poorer in MT-KO mice, suggesting an altered angiogenesis. To gain insight into the mechanisms involved, a number of cytokines and growth factors were evaluated. The number of cells expressing the proinflammatory cytokines IL-1β, IL-6, and TNF-α was higher in MT-KO mice than in normal mice, which was confirmed by RNase protection analysis, whereas the number of cells expressing the growth factors bFGF, TGFβ1, VEGF, and NT-3 was lower. Increased expression of proinflammatory cytokines could be involved in the sustained recruitment of CD-14+ and CD-34+ inflammatory cells and their altered functions observed in MT-KO mice. Decreases in trophic factors bFGF, TGFβ1, and VEGF could mediate the decreased angiogenesis and regeneration observed in MT-KO mice after the freeze lesion. A role for MT-I+II in angiogenesis was also observed in transgenic mice expressing IL-6 under the control of the promoter of glial fibrillary acidic protein gene (GFAP-IL6 mice) because MT-I+II deficiency dramatically decreased the IL-6-induced angiogenesis of the GFAP-IL6 mice. In situ hybridization analysis indicated that the MT-III expression was not altered by MT-I+II deficiency. These results suggest that the MT-I+II isoforms have major regulatory functions in the brain inflammatory response to injury, especially in the angiogenesis process.
The Novel β-Blocker, Carvedilol, Provides Neuroprotection in Transient Focal Stroke
Authors: Savitz Sean I. , Erhardt Joseph A. , Anthony James V. , Gupta Gaurav , Li Xiang , Barone Frank C. , Rosenbaum Daniel M.
Published: November 2003

Increasing evidence supports a role for oxidative stress, proinflammatory cytokines, and apoptosis in the pathophysiology of focal ischemic stroke. Previous studies have found that the multi-action drug, carvedilol, is a mixed adrenergic antagonist, and that it behaves as an antioxidant and inhibits apoptosis. In the current study, the authors investigated whether carvedilol provides protection in focal cerebral ischemia and whether this protection is associated with reduced apoptosis and the downregulation of the inflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). Male Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion (MCAO) by an intraluminal filament technique. Carvedilol (1, 3, and 10 mg/kg) was injected daily subcutaneously 2 or 4 days before the induction of ischemia. Neurologic scores, infarct volumes, TUNEL staining, and mRNA levels of TNF-α and IL-Iβ were assessed at 24 hours reperfusion. The effect of carvedilol on microvascular cortical perfusion was studied with continuous laser—Doppler flowmetry. Twenty-four hours after MCAO, carvedilol at all three doses reduced infarct volumes by at least 40% and reduced neurologic deficits on average by 40% compared with vehicle-treated controls when given 2 or 4 days before the induction of ischemia. This protection was not mediated by changes in temperature or blood flow. Treatment with all three dose regimens resulted in fewer TUNEL positive cells compared with controls. At 24 hours reperfusion, carvedilol decreased TNF-α and IL-1β expression by 40% to 50% in the ipsilateral ischemic cortex compared with the contralateral controls. The results of the current study indicate that carvedilol is neuroprotective in focal cerebral ischemia and may protect the ischemic brain by inhibiting apoptosis and attenuating the expression of TNF-α and IL-1β.
Regional Differences in Cerebral Vascular Response to Paco2 Changes in Humans Measured by Positron Emission Tomography
Authors: Ito Hiroshi , Yokoyama Ikuo , Iida Hidehiro , Kinoshita Toshibumi , Hatazawa Jun , Shimosegawa Eku , Okudera Toshio , Kanno Iwao
Published: November 2003

Hypercapnia and hypocapnia produce cerebral vasodilation and vasoconstriction, respectively. However, regional differences in the vascular response to changes in Paco2 in the human brain are not pronounced. In the current study, these regional differences were evaluated. In each of the 11 healthy subjects, cerebral blood flow (CBF) was measured using 15O-water and positron emission tomography at rest and during hypercapnia and hypocapnia. All CBF images were globally normalized for CBF and transformed into the standard brain anatomy. t values between rest and hypercapnia or hypocapnia conditions were calculated on a pixel-by-pixel basis. In the pons, cerebellum, thalamus, and putamen, significant relative hyperperfusion during hypercapnia was observed, indicating a large capacity for vasodilatation. In the pons and putamen, a significant relative hypoperfusion during hypocapnia, that is, a large capacity for vasoconstriction, was also observed, indicating marked vascular responsiveness. In the temporal, temporo-occipital, and occipital cortices, significant relative hypoperfusion during hypercapnia and significant relative hypoperfusion during hypocapnia were observed, indicating that cerebral vascular tone at rest might incline toward vasodilatation. Such regional heterogeneity of the cerebral vascular response should be considered in the assessment of cerebral perfusion reserve by hypercapnia and in the correction of CBF measurements for variations in subjects' resting Paco2.
Intrastriatal Transplantation of Bone Marrow Nonhematopoietic Cells Improves Functional Recovery After Stroke in Adult Mice
Authors: Li Yi , Chopp Michael , Chen Jieli , Wang Lei , Gautam Subhash C. , Xu Yong-Xian , Zhang Zhenggang
Published: November 2003

The authors transplanted adult bone marrow nonhematopoietic cells into the striatum after embolic middle cerebral artery occlusion (MCAO). Mice (n = 23; C57BL/6J) were divided into four groups: (1) mice (n = 5) were subjected to MCAO and transplanted with bone marrow nonhematopoietic cells (prelabeled by bromodeoxyuridine, BrdU) into the ischemic striatum, (2) MCAO alone (n = 8), (3) MCAO with injection of phosphate buffered saline (n = 5), and (4) bone marrow nonhematopoietic cells injected into the normal striatum (n = 5). Mice were killed at 28 days after stroke. BrdU reactive cells survived and migrated a distance of approximately 2.2 mm from the grafting areas toward the ischemic areas. BrdU reactive cells expressed the neuronal specific protein NeuN in 1% of BrdU stained cells and the astrocytic specific protein glial fibrillary acidic protein (GFAP) in 8% of the BrdU stained cells. Functional recovery from a rotarod test ( P < 0.05) and modified neurologic severity score tests (including motor, sensory, and reflex; P < 0.05) were significantly improved in the mice receiving bone marrow nonhematopoietic cells compared with MCAO alone. The current findings suggest that the intrastriatal transplanted bone marrow nonhematopoietic cells survived in the ischemic brain and improved functional recovery of adult mice even though infarct volumes did not change significantly. Bone marrow nonhematopoietic cells may provide a new avenue to promote recovery of injured brain.
Activation of Mitogen-Activated Protein Kinases After Permanent Cerebral Artery Occlusion in Mouse Brain
Authors: Wu Du-Chu , Ye Wen , Che Xiao-Ming , Yang Guo-Yuan
Published: November 2003

The purpose of this study was to examine the activation, topographic distribution, and cellular location of three mitogen-activated protein kinases (MAPKs) after permanent middle cerebral artery occlusion (MCAO) in mice. Phosphorylated MAPKs expression in the ischemic region was quantified using Western blot analysis and localized immunohistochemically using the diaminobenzide staining and double-labeled immunostaining. Extracellular signal-regulated kinases 1 and 2 (ERK1 and ERK2), p38 mitogen-activated protein (p38), and c-Jun NH2-terminal kinase or stress-activated protein kinase (SAPK/JNK) were initially activated at 30 minutes, 10 minutes, and 5 minutes, respectively, after focal cerebral ischemia. Peak expression represented a 2.7-fold, 3.7-fold, and 4.8-fold increase in each of these MAPKs, respectively. The immunohistochemical expressions of ERK1, ERK2, p38, and SAPK/JNK protein paralleled the Western blot analysis results. Double-labeled immunofluorescent staining demonstrated that the neurons and astrocytes expressed ERK1, ERK2, p38, and SAPK/JNK during the early time points after MCAO. The current results demonstrate that brain damage after ischemia rapidly triggers time-dependent ERK1, ERK2, p38, and SAPK/JNK phosphorylation, and reveals that neurons and astrocytes are involved in the activation of the MAPK pathway. This very early expression of MAPKs suggests that MAPKs may be closely involved in signal transduction during cerebral ischemia.
Early Detection of Irreversible Cerebral Ischemia in the Rat Using Dispersion of the Magnetic Resonance Imaging Relaxation Time, T1ρ
Authors: Gröhn Olli H J. , Kettunen Mikko I. , Mäkelä Heidi I. , Penttonen Markku , Pitkänen Asla , Lukkarinen Jouko A. , Kauppinen Risto A.
Published: November 2003

The impact of brain imaging on the assessment of tissue status is likely to increase with the advent of treatment methods for acute cerebral ischemia. Multimodal magnetic resonance imaging (MRI) demonstrates potential for selecting stroke therapy patients by identifying the presence of acute ischemia, delineating the perfusion defect, and excluding hemorrhage. Yet, the identification of tissue subject to reversible or irreversible ischemia has proven to be difficult. Here, the authors show that T1 relaxation time in the rotating frame, so-called T1ρ, serves as a sensitive MRI indicator of cerebral ischemia in the rat. The T1ρ prolongs within minutes after a drop in the CBF of less than 22 mL 100 g−1 min−1. Dependence of T1ρ on spin-lock amplitude, termed as T1ρ dispersion, increases by approximately 20% on middle cerebral artery (MCA) occlusion, comparable with the magnitude of diffusion reduction. The T1ρ dispersion change dynamically increases to be 38% ± 10% by the first 60 minutes of ischemia in the brain region destined to develop infarction. Following reperfusion after 45 minutes of MCA occlusion, the tissue with elevated T1ρ dispersion (yet normal diffusion) develops severe histologically verified neuronal damage; thus, the former parameter unveils an irreversible condition earlier than currently available MRI methods. The T1ρ dispersion as a novel MRI index of cerebral ischemia may be useful in determination of the therapeutic window for acute ischemic stroke.
Secondary Deterioration of Apparent Diffusion Coefficient After 1-Hour Transient Focal Cerebral Ischemia in Rats
Authors: Olah Laszlo , Wecker Stefan , Hoehn Mathias
Published: November 2003

Recent investigations on transient focal cerebral ischemia suggested recovery of energy metabolism during early reperfusion, but followed by secondary energy failure. As disturbances of energy metabolism are reflected by changes of the apparent diffusion coefficient (ADC) of water, the aim of the current study was to follow the dynamics of the ADC during 1 hour of middle cerebral artery occlusion (MCAO) and 10 hours of reperfusion. The right MCA was occluded in male Wistar rats inside the magnet using a remotely controlled thread occlusion model. Diffusion-, perfusion-, and T2-weighted images were performed repetitively, and ADC, perfusion, and T2maps were calculated and normalized to the respective preischemic value. The lesion volume at each time point was defined by ADC < 80% of control. At the end of 1-hour MCAO the hemispheric lesion volume was 22.3 ± 9.0%; it decreased to 6.4 ± 5.7% in the first 2 hours of reperfusion ( P < 0.01), but then increased again, and by the end of 10 hours of reperfusion reached 17.3 ± 9.3%. The mean relative ADC in the end ischemic lesion volume significantly improved within 2 hours of reperfusion (from 65.7 ± 1.2% to 90.1 ± 6.7% of control), but later declined and decreased to 75.4 ± 7.3% of control by the end of the experiment. Pixels with secondary deterioration of ADC showed a continuous increase of T2value during the first 2 hours of reperfusion in spite of ADC improvement, indicating improving cytotoxic, but generation of vasogenic edema during early reperfusion. A significant decrease of the perfusion level was not observed during 10 hours of recirculation. The authors conclude that the improvement of ADC in the early phase of reperfusion may be followed by secondary deterioration that was not caused by delayed hypoperfusion.
Effect of Thrombolysis on the Dynamics of Infarct Evolution After Clot Embolism of Middle Cerebral Artery in Mice
Authors: Hara Takayuki , Mies Günter , Hossmann Konstantin-Alexander
Published: November 2003

Reversible focal ischemia may lead to delayed tissue injury despite primary restoration of blood flow and metabolism. The authors investigated whether such delayed changes also occur after thrombolytic treatment of thromboembolic stroke. Clot embolism of the middle cerebral artery (MCA) was produced in C57/B16J mice by intracarotid injection of heterologous clots. One hour after embolism, one group was treated with intracarotid infusion of rt-PA (10 mg/kg). The untreated control group received an equal amount of vehicle. Just before onset of treatment and after 1, 3, 6, and 24 hours, animals were frozen in situ and cerebral blood flow (CBF), cerebral protein synthesis (CPS), ATP content, and DNA fragmentations (TUNEL) were imaged on cryostat sections using double tracer autoradiography, bioluminescence, and immunohistochemical techniques, respectively. In untreated animals (n = 20), CPS was suppressed in approximately 68% of hemispheric transsection at 1 hour after embolization. The ATP depleted area was smaller (approximately 58%), but between 6 and 24 hours it merged with that of CPS suppression. TUNEL-positive neurons became visible between 6 and 24 hours exclusively in regions with ATP depletion. rt-PA-induced thrombolysis (n = 20) led to the gradual improvement of blood flow. At 24 hours, ATP depletion was fully reversed and the CPS suppression area declined to approximately 16% of hemispheric transsection. Despite progressive metabolic recovery, large numbers of neurons became TUNEL-positive and animals died between 24 and 48 hours. Thrombolysis after clot embolism restores metabolic activity including protein synthesis, but the therapeutic benefit is limited by secondary injury that requires additional treatment to improve final outcome.