bluuebunny/crossref_metadata_2025 huggingface dataset:
Business portfolio restructuring, prior diversification posture and investor reactions
Authors: Byerly Robin T. , Lamont Bruce T. , Keasler Terrill
Published: November 2003

This study examined firm performance in market reaction to two types of business portfolio restructuring announcements: refocusing and repositioning. We predicted that market performance effects for these two types of strategic restructurers would be moderated by prior diversification posture. The theory behind these expectations was built on a general premise that restructuring strategy would be more favorably viewed by the market as performance enhancing when it offered greater potential for organizational transformation. Results showed strong support for our conclusion that prior diversification posture poses a significant contingency factor in restructuring firms' strategic choices. Further, the market tended to respond more favorably with this sample to repositioning restructuring choices. Copyright © 2003 John Wiley & Sons, Ltd.
Optimization of Internet Protocol network design and routing
Authors: Holmberg Kaj , Yuan Di
Published: November 2003

We consider network design and routing for Internet Protocol (IP) traffic. The design problem concerns capacity dimensioning of communication links, where the design cost consists of fixed charges and linear capacity expansion costs. The optimization problem also concerns determining the amount of traffic demand to be carried by the network and the metric used by a shortest path routing protocol. We present a novel linear mixed‐integer mathematical formulation and two heuristic solution procedures. The first heuristic uses mixed‐integer programming to generate a sequence of routing solutions. The second solution approach is a simulated annealing meta heuristic. Computational experiments for synthesized and real‐life networks show that high‐quality solutions can be obtained by both approaches. © 2003 Wiley Periodicals, Inc.
Prediction of deleterious functional effects of amino acid mutations using a library of structure‐based function descriptors
Authors: Herrgard Sanna , Cammer Stephen A. , Hoffman Brian T. , Knutson Stacy , Gallina Marijo , Speir Jeffrey A. , Fetrow Jacquelyn S. , Baxter Susan M.
Published: November 2003

An automated, active site‐focused, computational method is described for use in predicting the effects of engineered amino acid mutations on enzyme catalytic activity. The method uses structure‐based function descriptors (Fuzzy Functional Forms™ or FFFs™) to automatically identify enzyme functional sites in proteins. Three‐dimensional sequence profiles are created from the surrounding active site structure. The computationally derived active site profile is used to analyze the effect of each amino acid change by defining three key features: proximity of the change to the active site, degree of amino acid conservation at the position in related proteins, and compatibility of the change with residues observed at that position in similar proteins. The features were analyzed using a data set of individual amino acid mutations occurring at 128 residue positions in 14 different enzymes. The results show that changes at key active site residues and at highly conserved positions are likely to have deleterious effects on the catalytic activity, and that non‐conservative mutations at highly conserved residues are even more likely to be deleterious. Interestingly, the study revealed that amino acid substitutions at residues in close contact with the key active site residues are not more likely to have deleterious effects than mutations more distant from the active site. Utilization of the FFF‐derived structural information yields a prediction method that is accurate in 79–83% of the test cases. The success of this method across all six EC classes suggests that it can be used generally to predict the effects of mutations and nsSNPs for enzymes. Future applications of the approach include automated, large‐scale identification of deleterious nsSNPs in clinical populations and in large sets of disease‐associated nsSNPs, and identification of deleterious nsSNPs in drug targets and drug metabolizing enzymes. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Bound states of multipoles
Authors: Pupyshev Vladimir I. , Ermilov Alexandr Y.
Published: November 2003

For the classical point‐charge systems, such as two‐point dipole, linear and planar square quadrupoles, and cubic octupole, the critical‐charge values, which ensure the existence of the bound states in the one‐electron problem, are determined numerically within both the linear combination of atomic orbital and the finite‐difference approximations. The methods of the critical parameters calculation for the problem of the discrete spectrum state embedding into the continuum are considered. The estimated critical‐charge values for the square quadrupole and the cubic octupole (with unit side and edge, respectively) are estimated to be 1.6516 and 1.7257 a.u., respectively. The qualitative analysis of the problem is also presented. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Hartree–Fock calculations of electronic structure of (110)‐surface of rutile TiO2: Comparison of single (2D) and periodic (3D) slab models
Authors: Evarestov R. A. , Bandura A. V.
Published: November 2003

Two different slab models are used in calculations of the surface phenomena: two‐dimensional (2D) single (isolated) slab model (with 2D periodicity) and three‐dimensional (3D)‐slab model (with slabs, periodically repeated along the normal to the surface). Here we present the investigation and comparison of these two models basing on calculations of the (110) rutile surface within the same computational scheme (Hartree–Fock linear combination of atomic orbitals approach). The convergence of calculated surface energy and Fermi level is studied with the change of slab thickness and interslab vacuum gap using both pseudopotential and all‐electron calculations. It is found that Durand–Barthelat pseudopotentials with diffuse d‐functions on Ti atoms lead to the incorrect results for surface energy and Fermi level of 3D‐slab model. Inclusion of the core electrons in 3D‐slab calculations and the use of the 2D‐supercell approach allow obtaining surface energy in quantitative agreement with that obtained in 2D‐slab all‐electron calculations. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
PROPRIÉTAIRES ET COMMERÇANTS AFRICAINS À OUAGADOUGOU ET À BOBO-DIOULASSO (HAUTE-VOLTA), FIN 19ÈME SIÈCLE–1960
Authors: FOURCHARD LAURENT
Published: November 2003

A partir de sources orales et d'archives foncières, fiscales et administratives, cet essai sur la propriété africaine rend compte des pratiques foncières, résidentielles et sociales d'un groupe de commerçants africains qui investirent, durant la période coloniale, les quartiers européens de Ouagadougou et de Bobo-Dioulasso en Haute-Volta. La comparaison de ces villes inégalement insérées dans les circuits de l'économie coloniale renseigne sur les marges de manœuvre de ces commerçants, et notamment de leurs aptitudes à jouer des différentes réglementations foncières alors en vigueur. Au-delà des comportements collectifs qui révèlent généralement un double investissement résidentiel (centre européen/quartiers africains), les stratégies individuelles témoignent des liens fréquents entre l'assise foncière des propriétaires, leur envergure sociale et leur rôle politico-administratif.
Present‐day crustal deformation around Sagaing fault, Myanmar
Authors: Vigny Christophe , Socquet Anne , Rangin Claude , Chamot‐Rooke Nicolas , Pubellier Manuel , Bouin Marie‐Noëlle , Bertrand Guillaume , Becker M.
Published: November 2003

Global Positioning System (GPS) measurement campaigns in Myanmar, conducted in 1998 and 2000, allow quantifying the present‐day crustal deformation around the Sagaing fault system in central Myanmar. Both a regional network installed at four points within the country and a local 18‐station network centered on the city of Mandalay across the Sagaing fault demonstrate that active deformation related to the northward motion of India is distributed across Myanmar in a platelet that extends from the western edge of the Shan Plateau in the east to the Andaman Trench in the west. In this platelet, deformation is rather diffuse and distributed over distinct fault systems. In the east, the Sagaing/Shan Scarp fault system absorbs <20 mm/yr of the 35 mm/yr India/Sundaland strike‐slip motion. Along this major plate boundary, strain is partitioned along the N‐S trending Sagaing fault and the transtensile N160°E trending Shan Scarp fault. Shortening and wrenching within the inverted central Myanmar basins, strike‐slip faults affecting the Arakan Yoma fold‐and‐thrust belt, and oblique subduction along the Andaman trench should absorb the remaining India/Sundaland motion (>10 mm/yr). This GPS study combined with an on land geotectonic survey demonstrate that oblique slip of India along the rigid Sundaland block is accommodated by a partitioned system characterized by distribution of deformation over a wide zone.
Total hydrogen mixing ratio anomaly around the mesopause region
Authors: Sonnemann G. R. , Körner U.
Published: November 2003

The strong turbulent mixing within the middle atmosphere should prevent a change of the value of the total hydrogen mixing ratio regardless of the transformation of the hydrogen species in one another within the homosphere. Within the heterosphere the corresponding mixing ratio should drastically increase due to the action of molecular diffusion. We show on the basis of a global three‐dimensional model of the dynamics and chemistry of the middle atmosphere that the total mixing ratio decreases under certain conditions when an (escape) flux flows through the domain. The effect occurs particularly above and around the mesopause region, reaching a distinct minimum at about 108 km height. Hunten and Strobel [1974] also found a small reduction on the basis of simplified model calculations, but they stated that the total mixing ratio of hydrogen atoms remains nearly the same. The cause of this apparently paradoxical behavior lies in the fact that under the condition of a hydrogen flux just in the domain of transition of predominant turbulent diffusion to predominant molecular diffusion, a strong decomposition of the heavier H2O component into the light hydrogen constituents takes place, and the temperature increases strongly with height above the mesopause. The marked reduction of the total hydrogen mixing ratio within the extended mesopause region is extremely important for all questions concerning the physics and chemistry of this domain.
Smn, the spinal muscular atrophy–determining gene product, modulates axon growth and localization of β-actin mRNA in growth cones of motoneurons
Authors: Rossoll Wilfried , Jablonka Sibylle , Andreassi Catia , Kröning Ann-Kathrin , Karle Kathrin , Monani Umrao R. , Sendtner Michael
Published: November 2003

Spinal muscular atrophy (SMA), a common autosomal recessive form of motoneuron disease in infants and young adults, is caused by mutations in the survival motoneuron 1 (SMN1) gene. The corresponding gene product is part of a multiprotein complex involved in the assembly of spliceosomal small nuclear ribonucleoprotein complexes. It is still not understood why reduced levels of the ubiquitously expressed SMN protein specifically cause motoneuron degeneration. Here, we show that motoneurons isolated from an SMA mouse model exhibit normal survival, but reduced axon growth. Overexpression of Smn or its binding partner, heterogeneous nuclear ribonucleoprotein (hnRNP) R, promotes neurite growth in differentiating PC12 cells. Reduced axon growth in Smn-deficient motoneurons correlates with reduced β-actin protein and mRNA staining in distal axons and growth cones. We also show that hnRNP R associates with the 3′ UTR of β-actin mRNA. Together, these data suggest that a complex of Smn with its binding partner hnRNP R interacts with β-actin mRNA and translocates to axons and growth cones of motoneurons.
Superoxide Dismutases inCandida albicans: Transcriptional Regulation and Functional Characterization of the Hyphal-inducedSOD5Gene
Authors: Martchenko Mikhail , Alarco Anne-Marie , Harcus Doreen , Whiteway Malcolm
Published: November 2003

Superoxide dismutases (SOD) convert superoxide radicals into less damaging hydrogen peroxide. The opportunistic human pathogen Candida albicans is known to express CuZnSOD (SOD1) and MnSOD (SOD3) in the cytosol and MnSOD (SOD2) in the mitochondria. We identified three additional CuZn-containing superoxide dismutases, SOD4, SOD5, and SOD6, within the sequence of the C. albicans genome. The transcription of SOD5 was up-regulated during the yeast to hyphal transition of C. albicans, and SOD5 was induced when C. albicans cells were challenged with osmotic or with oxidative stresses. SOD5 transcription was also increased when cells were grown on nonfermentable substrates as the only carbon source. The Rim101p transcription factor was required for all inductions observed, whereas the Efg1p transcription factor was specifically needed for serum-modulated expression. Deletion of SOD5 produced a viable mutant strain that showed sensitivity to hydrogen peroxide when cells were grown in nutrient-limited conditions. Sod5p was found to be necessary for the virulence of C. albicans in a mouse model of infection. However, the sod5 mutant strain showed the same resistance to macrophage attack as its parental strain, suggesting that the loss of virulence in not due to an increased sensitivity to macrophage attack.
Fusion between Phagosomes, Early and Late Endosomes: A Role for Actin in Fusion between Late, but Not Early Endocytic Organelles
Authors: Kjeken Rune , Egeberg Morten , Habermann Anja , Kuehnel Mark , Peyron Pascale , Floetenmeyer Matthias , Walther Paul , Jahraus Andrea , Defacque Hélène , Kuznetsov Sergei A. , Griffiths Gareth
Published: November 2003

Actin is implicated in membrane fusion, but the precise mechanisms remain unclear. We showed earlier that membrane organelles catalyze the de novo assembly of F-actin that then facilitates the fusion between latex bead phagosomes and a mixture of early and late endocytic organelles. Here, we correlated the polymerization and organization of F-actin with phagosome and endocytic organelle fusion processes in vitro by using biochemistry and light and electron microscopy. When membrane organelles and cytosol were incubated at 37°C with ATP, cytosolic actin polymerized rapidly and became organized into bundles and networks adjacent to membrane organelles. By 30-min incubation, a gel-like state was formed with little further polymerization of actin thereafter. Also during this time, the bulk of in vitro fusion events occurred between phagosomes/endocytic organelles. The fusion between latex bead phagosomes and late endocytic organelles, or between late endocytic organelles themselves was facilitated by actin, but we failed to detect any effect of perturbing F-actin polymerization on early endosome fusion. Consistent with this, late endosomes, like phagosomes, could nucleate F-actin, whereas early endosomes could not. We propose that actin assembled by phagosomes or late endocytic organelles can provide tracks for fusion-partner organelles to move vectorially toward them, via membrane-bound myosins, to facilitate fusion.
Regulated Exocytosis in Neuroendocrine Cells: A Role for Subplasmalemmal Cdc42/N-WASP-induced Actin Filaments
Authors: Gasman Stéphane , Chasserot-Golaz Sylvette , Malacombe Magali , Way Michael , Bader Marie-France
Published: November 2003

In neuroendocrine cells, actin reorganization is a prerequisite for regulated exocytosis. Small GTPases, Rho proteins, represent potential candidates coupling actin dynamics to membrane trafficking events. We previously reported that Cdc42 plays an active role in regulated exocytosis in chromaffin cells. The aim of the present work was to dissect the molecular effector pathway integrating Cdc42 to the actin architecture required for the secretory reaction in neuroendocrine cells. Using PC12 cells as a secretory model, we show that Cdc42 is activated at the plasma membrane during exocytosis. Expression of the constitutively active Cdc42L61mutant increases the secretory response, recruits neural Wiskott-Aldrich syndrome protein (N-WASP), and enhances actin polymerization in the subplasmalemmal region. Moreover, expression of N-WASP stimulates secretion by a mechanism dependent on its ability to induce actin polymerization at the cell periphery. Finally, we observed that actin-related protein-2/3 (Arp2/3) is associated with secretory granules and that it accompanies granules to the docking sites at the plasma membrane upon cell activation. Our results demonstrate for the first time that secretagogue-evoked stimulation induces the sequential ordering of Cdc42, N-WASP, and Arp2/3 at the interface between granules and the plasma membrane, thereby providing an actin structure that makes the exocytotic machinery more efficient.
p38α Mitogen-activated Protein Kinase Sensitizes Cells to Apoptosis Induced by Different Stimuli
Authors: Porras Almudena , Zuluaga Susana , Black Emma , Valladares Amparo , Alvarez Alberto M. , Ambrosino Concetta , Benito Manuel , Nebreda Angel R.
Published: November 2003

p38α mitogen-activated protein (MAP) kinase is a broadly expressed signaling molecule that participates in the regulation of cellular responses to stress as well as in the control of proliferation and survival of many cell types. We have used cell lines derived from p38α knockout mice to study the role of this signaling pathway in the regulation of apoptosis. Here, we show that cardiomyocytes and fibroblasts lacking p38α are more resistant to apoptosis induced by different stimuli. The reduced apoptosis of p38α-deficient cells correlates with decreased expression of the mitochondrial proapoptotic protein Bax and the apoptosis-inducing receptor Fas/CD-95. Cells lacking p38α also have increased extracellular signal-regulated kinase (ERKs) MAP kinase activity, and the up-regulation of this survival pathway seems to be at least partially responsible for the reduced levels of apoptosis in the absence of p38α. Phosphorylation of the transcription factor STAT3 on Ser-727, mediated by the extracellular signal-regulated kinase MAP kinase pathway, may contribute to the decrease in both Bax and Fas expression in p38α-/- cells. Thus, p38α seems to sensitize cells to apoptosis via both up-regulation of proapoptotic proteins and down-regulation of survival pathways.
Sympathoadrenal Modulation of Stress-Activated Signaling in Burn Trauma
Authors: Ballard-Croft Cherry , Horton Jureta W.
Published: November 2003

Burn injury stimulates stress-responsive components, p38 mitogen-activated protein kinase (MAPK)/c-Jun N-terminal kinases (JNK)/nuclear factor (NF)-κB. p38 MAPK plays a role in postburn cardiomyocyte tumor necrosis factor-α secretion and cardiac dysfunction. Since burn trauma increases circulating catecholamine levels, which in turn modulate inflammatory cytokine production, we hypothesized that increased sympathetic activity after major burn trauma may trigger postburn cardiac p38 MAPK activation via an adrenergic receptor-mediated phenomenon. We examined adrenergic receptor populations involved in burn-activated cardiac stress signaling. Sprague Dawley rats were divided into six groups: 1) control, 2) control plus α1-adrenergic agonist phenylephrine (2 μg/kg, intravenous), 3) control plus β-adrenergic agonist isoproterenol (1 μg/kg, intravenous), 4) burn (fluid resuscitation with lactated Ringer's 4 ml/kg/% burn), 5) burn plus α1-adrenergic antagonist prazosin (1 mg/kg, by mouth), and 6) burn plus β-adrenergic antagonist propranolol (3.3 mg/kg, by mouth). Phenylephrine, but not isoproterenol, increased cardiac p38 MAPK/JNK/NF-κB activation. Burn trauma activated p38 MAPK, JNK, and NF-κB, and this stress response was blocked by either prazosin or propranolol. Thus, stimulation of the adrenergic pathway may constitute one upstream activator of stress response in burn.
Cecal Perforation in Thermal Injury
Authors: Moore Laura J. , Patel Subash , Kowal-Vern Areta , Latenser Barbara A.
Published: November 2003

Gastrointestinal complications in burn patients include ileus, constipation, hemorrhage from ulcerations, ischemic bowel, and rarely, perforations. Patients with hypotensive episodes and sepsis are at risk for developing ischemic bowel disease. There have been three reports in the literature of cecal perforation in burn patients. We present an additional case and review of the literature.
Simultaneous Measurement of Salicylate Hydroxylation and Glutamate Release in the Penumbral Cortex following Transient Middle Cerebral Artery Occlusion in Rats
Authors: Morimoto Tadashi , Globus Mordecai Y.-T. , Busto Raul , Martinez Elena , Ginsberg Myron D.
Published: November 2003

Using the microdialysis technique and laser-Doppler flowmetry, we performed simultaneous measurement of salicylate hydroxylation and glutamate release along with local CBF in the ischemic penumbral cortex of rat brain subjected to normothermic transient middle cerebral artery (MCA) occlusion. Cortical CBF fell to 24 ± 11% (mean ± SD) during ischemia and recovered to 84 ± 16% during reperfusion. Extracellular glutamate levels increased by 6.5-fold above baseline 10 min following MCA occlusion but subsequently returned to near baseline levels in spite of the persistent ischemia. Increase in 2,3- and 2,5-dihydroxybenzoic acid (DHBA) concentrations in the microdialysis perfusate was confirmed during both ischemia and reperfusion phase. Although the temporal profile and amount of salicylate hydroxylation were heterogeneous among individual animals, integrated 2,3-DHBA concentrations during reperfusion were correlated positively with integrated glutamate concentrations during ischemia and negatively with mean postischemic CBF. These relationships suggest a possible association of the enhanced production of 2,3-DHBA during reperfusion with larger amounts of intraischemic glutamate release and lower levels of postischemic CBF.
Laser-Doppler Evaluation of Rat Brain Microcirculation: Comparison with the [14C]-Iodoantipyrine Method Suggests Discordance during Cerebral Blood Flow Increases
Authors: Fabricius Martin , Lauritzen Martin
Published: November 2003

Laser-Doppler flowmetry (LDF) is very popular for measurements of dynamic changes of cerebral blood flow (CBF). We studied whether changes of CBF measured by LDF correlate with CBF measured by the [14C]iodoantipyrine (IAP) technique in the range relevant for most physiological experiments (—30– + 130%). LDF was recorded biparietally by two laser-Doppler probes in halothane-anesthetized rats. Absolute CBF was measured in tissue samples of both parietal cortices after [14C]iodoantipyrine was given i.v. CBF of one hemisphere was reduced by an episode of cortical spreading depression (CSD), which markedly reduces the responsiveness of the ipsilateral cortical CBF to vasoactive stimuli for up to 30 min, while CBF regulation of the contralateral cortex remains intact. CBF was measured under normoventilated, hypercapnic, and hypoxic conditions. The relative changes of CBF measured by the LDF technique were independent of the preceding baseline LDF value. Absolute CBFIAP values correlated poorly to the simultaneously recorded arbitrary LDF values ( r = 0.44). In contrast, the ratio of CBFIAP values correlated with the ratio of the relative LDF changes between the two hemispheres ( p < 0.001). At reduced CBF, no significant difference was found between methods. At increased CBF, however, LDF was greater than CBFIAP, as indicated by a slope of correlation of 1.45 ( p < 0.005).
Cortical Spreading Depression Protects against Subsequent Focal Cerebral Ischemia in Rats
Authors: Matsushima Kazushi , Hogan Matthew J. , Hakim Antoine M.
Published: November 2003

The possibility that cortical spreading depression (CSD) may have neuroprotective action during subsequent focal cerebral ischemia was examined in rats. Three days before the imposition of focal cerebral ischemia CSDs were elicited by applying potassium chloride (KCl) for 2 h through a microdialysis probe implanted in the occipital cortex. Control animals were handled identically except that saline was infused instead of KCl. Focal ischemia was produced by the intraluminal suture method and cortical and subcortical infarct volumes were measured 7 days later. Neocortical infarct volume was reduced from 124.8 ± 49.5 mm3 in the controls to 62.9 ± 59.5 mm3 in the animals preconditioned with CSD (p = 0.012). There was no difference between the two groups in the subcortical infarct volume or in CBF, measured by the hydrogen clearance method, during or immediately after the ischemic interval. Our data indicate that preconditioning CSD applied 3 days before middle cerebral artery occlusion may increase the brain's resistance to focal ischemic damage and may be used as a model to explore the neuroprotective molecular responses of neuronal and glial cells.
Mild Posttraumatic Hypothermia Reduces Mortality after Severe Controlled Cortical Impact in Rats
Authors: Clark Robert S. B. , Kochanek Patrick M. , Marion Donald W. , Schiding Joanne K. , White Melissa , Palmer Alan M. , DeKosky Steven T.
Published: November 2003

The effect of posttraumatic hypothermia (brain temperature controlled at 32°C for 4 h) on mortality after severe controlled cortical impact (CCI) was studied in rats. Four posttraumatic brain temperatures were compared: 37°C (n = 10), 36°C (n = 4), 32°C (n = 10), and uncontrolled (UC; n = 6). Rats were anesthetized and subjected to severe CCI (4.0-m/s velocity, 3.0-mm depth) to the exposed left parietal cortex. At 10 min posttrauma the rats were cooled or maintained at their target brain temperature, using external cooling or warming. Brain temperature in the UC group was recorded but not regulated, and rectal temperature was maintained at 37 ± 0.5°C. After 4 h, rats were rewarmed over a 1-h period to 37°C, extubated, and observed for 24 h. In the 37 and 36°C groups, 24-h mortality was 50% (37°C = 5/10, 36°C = 2/4). In the 32°C group, 24-h mortality was 10% (1/10). In the UC group, brain temperature was 35.4 ± 0.6°C during the 4-h treatment period and 24-h mortality was 0% (0/6). Mortality was higher in groups with brain temperatures ≥36°C versus those with brain temperatures <36°C (50 vs. 6%, respectively; p < 0.05). Additionally, electroencephalograms (EEG) were recorded in subsets of each temperature group and the percentage of time that the EEG was suppressed (isoelectric) was determined. Percentage of EEG suppression was greater in the hypothermic (32°C, n = 6; UC, n = 4) groups than in the normothermic(36°C, n = 3; 37°C, n = 6) groups (23.3 ± 14.3 vs. 1.2 ± 3.1%, respectively; p < 0.05). Posttraumatic hypothermia suppressed EEG during treatment and reduced mortality after severe CCI. The threshold for this protective effect appears to be a brain temperature <36°C. Thus, even mild hypothermia may be beneficial after severe brain trauma.
Middle Cerebral Artery Occlusion in Wistar and Fischer-344 Rats: Functional and Morphological Assessment of the Model
Authors: Herz Richard C. G. , Jonker Marcel , Verheul Hieronymus B. , Hillen Berend , Versteeg Dirk H. G. , de Wildt Dick J.
Published: November 2003

Cerebral infarction volume after occlusion of a short proximal segment of the middle cerebral artery (MCA) is reported to be different in Wistar compared to Fischer-344 (F344) rats, in both size and variability. Knowledge about the cause of these differences might enable us to explain and perhaps reduce the variation in infarct volume and create a reproducible model of focal cerebral ischemia in the rat. We investigated in Wistar and F344 rats both the effect of occlusion of a long proximal MCA segment on cerebral infarction volume, visualized by magnetic resonance imaging and histology, and the morphology of the major cerebral arteries. Occlusion of a long proximal MCA segment resulted in a striatal and a small cortical infarction in Wistar and a striatal and sizable cortical infarction in F344 rats (as is the case after occlusion of a short proximal MCA segment). In Wistar rats, however, occlusion of a long proximal MCA segment strongly reduced the variability in infarction volume in comparison to occlusion of a small proximal MCA segment. Analysis of the morphology of the major cerebral arteries showed a significantly higher number of proximal side branches of the long proximal MCA segment in Wistar rats than in F344 rats. We conclude that after short-segment proximal MCA occlusion, extreme variability in cerebral infarction volume in Wistar rats compared to F344 rats may be attributable to a significantly greater number of proximal MCA side branches in Wistar rats than F344 rats.
Non-Invasive Neurochemical Analysis of Focal Excitotoxic Lesions in Models of Neurodegenerative Illness Using Spectroscopic Imaging
Authors: Jenkins Bruce G. , Brouillet Emmanuel , Chen Yin-Ching I. , Storey Elsdon , Schulz Jörg B. , Kirschner Pamela , Beal M. Flint , Rosen Bruce R.
Published: November 2003

Water-suppressed chemical shift magnetic resonance imaging was used to detect neurochemical alterations in vivo in neurotoxin-induced rat models of Huntington's and Parkinson's disease. The toxins were: N-methyl-4-phenylpyridinium (MPP+), aminooxyacetic acid (AOAA), 3-nitropropionic acid (3-NP), malonate, and azide. Local or systemic injection of these compounds caused secondary excitotoxic lesions by selective inhibition of mitochondrial respiration that gave rise to elevated lactate concentrations in the striatum. In addition, decreased N-acetylaspartate (NAA) concentrations were noted at the lesion site over time. Measurements of lactate washout kinetics demonstrated that t1/2 followed the order: 3-NP ≈ MPP+ » AOAA ≈ malonate, which parallels the expected lifetimes of the neurotoxins based on their mechanisms of action. Further increases in lactate were also caused by intravenous infusion of glucose. At least part of the excitotoxicity is mediated through indirect glutamate pathways because lactate production and lesion size were diminished using unilateral decortectomies (blockade of glutamatergic input) or glutamate antagonists (MK-801). Lesion size and lactate were also diminished by energy repletion with ubiquinone and nicotinamide. Lactate measurements determined by magnetic resonance agreed with biochemical measurements made using freeze clamp techniques. Lesion size as measured with MR, although larger by 30%, agreed well with lesion size determined histologically. These experiments provide evidence for impairment of intracellular energy metabolism leading to indirect excitotoxicity for all the compounds mentioned before and demonstrate the feasibility of small-volume metabolite imaging for in vivo neurochemical analysis.
Antibodies against Adhesion Molecules Reduce Apoptosis after Transient Middle Cerebral Artery Occlusion in Rat Brain
Authors: Chopp Michael , Li Yi , Jiang Ning , Zhang Rui Lan , Prostak Jonathan
Published: November 2003

We tested the hypothesis that treatment of transient focal cerebral ischemia in rat with antibodies directed against adhesion molecules reduces apoptosis. Rats (n = 31) were subjected to 2 h of middle cerebral artery (MCA) occlusion induced by intraluminal insertion of a nylon monofilament into the internal carotid artery. Upon reperfusion, animals were treated with monoclonal antibodies directed against intercellular adhesion molecule (ICAM)-1) (n = 8) or integrin CD11b/CD18 (n = 10), or administered IgG1 as a control (n = 13). At 48 h after ischemia, animals were killed and the brains analyzed for ischemic cell damage, using hematoxylin and eosin (H/E); apoptosis, using the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) method; and inflammatory cells, using immunohistochemistry with an anti-myeloperoxidase (MPO) antibody. Data revealed a significant reduction in the volume of infarction ( p < 0.01) and a decline in the absolute ( p < 0.001), and normalized (to the ischemic area, p < 0.05) numbers of apoptotic cells in both animals treated with anti-ICAM-1 and anti-CD11b antibodies compared to control animals. The numbers of immunoreactive MPO cells were also reduced in the treatment groups compared to those in the control group ( p < 0.05). These data suggest that treatment with anti-adhesion molecule antibodies selectively reduce apoptosis, and that a contributing factor to the beneficial effect of antibody treatment for reducing ischemic cell damage may be a reduction in numbers of apoptotic cells.
Metyrapone, an Inhibitor of Glucocorticoid Production, Reduces Brain Injury Induced by Focal and Global Ischemia and Seizures
Authors: Smith-Swintosky Virginia L. , Pettigrew L. Creed , Sapolsky Robert M. , Phares Chris , Craddock Susan D. , Brooke Sheila M. , Mattson Mark P.
Published: November 2003

Increasing evidence indicates that glucocorticoids (GCs), produced in response to physical/emotional stressors, can exacerbate brain damage resulting from cerebral ischemia and severe seizure activity. However, much of the supporting evidence has come from studies employing nonphysiological paradigms in which adrenalectomized rats were compared with those exposed to constant GC concentrations in the upper physiological range. Cerebral ischemia and seizures can induce considerable GC secretion. We now present data from experiments using metyrapone (an 11-β-hydroxylase inhibitor of GC production), which demonstrate that the GC stress-response worsens subsequent brain damage induced by ischemia and seizures in rats. Three different paradigms of brain injury were employed: middle cerebral artery occlusion (MCAO) model of focal cerebral ischemia; four-vessel occlusion (4VO) model of transient global forebrain ischemia; and kainic acid (KA)-induced (seizure-mediated) excitotoxic damage to hippocampal CA3 and CA1 neurons. Metyrapone (200 mg/kg body wt) was administered systemically in a single i.p. bolus 30 min prior to each insult. In the MCAO model, metyrapone treatment significantly reduced infarct volume and also preserved cells within the infarct. In the 4VO model, neuronal loss in region CA1 of the hippocampus was significantly reduced in rats administered metyrapone. Seizure-induced damage to hippocampal pyramidal neurons (assessed by cell counts and immunochemical analyses of cytoskeletal alterations) was significantly reduced in rats administered metyrapone. Measurement of plasma levels of corticosterone (the species-typical GC of rats) after each insult showed that metyrapone significantly suppressed the injury-induced rise in levels of circulating corticosterone. These findings indicate that endogenous corticosterone contributes to the basal level of brain injury resulting from cerebral ischemia and excitotoxic seizure activity and suggest that drugs that suppress glucocorticoid production may be effective in reducing brain damage in stroke and epilepsy patients.
ARL 17477, a Potent and Selective Neuronal NOS Inhibitor Decreases Infarct Volume after Transient Middle Cerebral Artery Occlusion in Rats
Authors: Zhang Zheng G. , Reif David , Macdonald James , Tang Wen Xue , Kamp Dietgard K. , Gentile Robert J. , Shakespeare William C. , Murray Robert J. , Chopp Michael
Published: November 2003

We tested the effects of administration of a selective neuronal nitric oxide synthase (nNOS) inhibitor, ARL 17477, on ischemic cell damage and regional cerebral blood flow (rCBF), in rats subjected to transient (2 h) middle cerebral artery (MCA) occlusion and 166 h of reperfusion (n = 48) and in rats without MCA occlusion (n = 25), respectively. Animals were administered ARL 17477 (i.v.): 10 mg/kg; 3 mg/kg; 1 mg/kg; N-nitro-L-arginine (L-NA) 10 mg/kg L-NA 1 mg/kg; and Vehicle. Administration of ARL 17477 1 mg/kg, 3 mg/kg and 10 mg/kg reduced ischemic infarct volume by 53 (p < 0.05), 23, and 6.5%, respectively. L-NA 1 mg/kg and 10 mg/kg increased infarct volume by 2 and 15%, respectively (p > 0.05). Administration of ARL 17477 (10 mg/kg) significantly (p < 0.05) decreased rCBF by 27 ± 5.3 and 24 ± 14.08% and cortical NOS activity by 86 ± 14.9 and 91 ± 8.9% at 10 min or 3 h, respectively, and did not alter mean arterial blood pressure (MABP). L-NA (10 mg/kg) significantly reduced rCBF by 23 ± 9.8% and NOS activity by 81 ± 7% and significantly (p < 0.05) increased MABP. Treatment with 3 mg/kg and 1 mg/kg ARL 17477 reduced rCBF by only 2.4 ± 4.5 and 0%, respectively, even when NOS activity was reduced by 63 ± 13.4 and 45 ± 15.7% at 3 h, respectively, (p < 0.05). The data demonstrate that ARL 17477 inhibits nNOS in the rat brain and causes a dose-dependent reduction in infarct volume after transient MCA occlusion.
Simultaneous Intracerebral Microdialysis and Positron Emission Tomography in the Detection of Ischemia in Patients with Subarachnoid Hemorrhage
Authors: Enblad Per , Valtysson Johann , Andersson Jesper , Lilja Anders , Valind Sven , Antoni Gunnar , Långström Bengt , Hillered Lars , Persson Lennart
Published: November 2003

Intracerebral microdialysis (MD) was applied in patients with subarachnoid hemorrhage. The regional CBF, the CMRO2, and oxygen extraction ratio (OER) were measured with simultaneous positron emission tomography (PET). The aim was to directly correlate alterations in dialysate levels of energy-related metabolites (lactate, lactate/pyruvate ratio, hypoxanthine) and excitatory amino acids (EAAs) (glutamate and aspartate) to the energy state in the MD probe region as determined by PET. Regional ischemia was defined according to Heiss et al. and Lassen ( Heiss et al., 1992 ; Lassen, 1966 ). Whole-brain ischemia was considered present when the OER for the whole brain exceeded the mean whole-brain OER + 2 SD of six reference patients. In general, the presence of whole-brain ischemia and/or regional ischemia within the region of the MD probe was associated with increased levels of energy-related metabolites and EAAs retrieved by MD. Increased levels of energy-related metabolites and EAAs were only occasionally seen when PET did not show any signs of ischemia or when signs of regional ischemia were found remote from the MD probe region. Thus, the energy-related metabolites and EAAs may be used as extracellular “markers” of ischemia. PET may be of use in defining critical ischemic regions (tissue at risk) where the MD probe can be inserted for- chemical monitoring.
Functional Mapping of Human Sensorimotor Cortex with 3D BOLD fMRI Correlates Highly with H215O PET rCBF
Authors: Ramsey Nick F. , Kirkby Brenda S. , Van Gelderen Peter , Berman Karen F. , Duyn Jeff H. , Frank Joe A. , Mattay Venkata S. , Van Horn John D. , Esposito Giuseppe , Moonen Chrit T. W. , Weinberger Daniel R.
Published: November 2003

Positron emission tomography (PET) functional imaging is based on changes in regional cerebral blood flow (rCBF). Functional magnetic resonance imaging (fMRI) is based on a variety of physiological parameters as well as rCBF. This study is aimed at the cross validation of three-dimensional (3D) fMRI, which is sensitive to changes in blood oxygenation, with oxygen-15-labeled water (H215O) PET. Nine normal subjects repeatedly performed a simple finger opposition task during fMRI scans and during PET scans. Within-subject statistical analysis revealed significant (“activated”) signal changes ( p < 0.05, Bonferroni corrected for number of voxels) in contralateral primary sensorimotor cortex (PSM) in all subjects with fMRI and with PET. With both methods, 78% of all activated voxels were located in the PSM. Overlap of activated regions occurred in all subjects (mean 43%, SD 26%). The size of the activated regions in PSM with both methods was highly correlated ( rho = 0.87, p < 0.01). The mean distance between centers of mass of the activated regions in the PSM for fMRI versus PET was 6.7 mm (SD 3.0 mm). Average magnitude of signal change in activated voxels in this region, expressed as z-values adapted to timeseries, zt, was similar (fMRI 5.5, PET 5.3). Results indicate that positive blood oxygen level-dependent (BOLD) signal changes obtained with 3D principles of echo shifting with a train of observations (PRESTO) fMRI are correlated with rCBF, and that sensitivity of fMRI can equal that of H215O PET.
Calcium Movement in Ischemia-Tolerant Hippocampal CA1 Neurons after Transient Forebrain Ischemia in Gerbils
Authors: Ohta Shinsuke , Furuta Shigeru , Matsubara Ichiro , Kohno Keiji , Kumon Yoshiaki , Sakaki Saburo
Published: November 2003

Hippocampal CA1 neurons exposed to a nonlethal period (2 min) of ischemia, acquired tolerance to a subsequent lethal 5-min period of ischemia, which usually causes delayed-type neuronal death. Intracelluar Ca2+ movements before and after the 5 min of forebrain ischemia were evaluated in gerbil hippocampal CA1 pyramidal neurons, had acquired tolerance in comparison with nonischemia-tolerant CA1 neurons. Evaluation was performed by observing the ultrastructural intracellular Ca2+ distribution and the Ca2+ adenosine triphosphatase (Ca2+-ATPase) activity using electron microscopic cytochemistry. In comparison with nonischemia-tolerant CA1 neurons, mitochondria of ischemia-tolerant CA1 neurons sequestered more Ca2+ from the cytosomal fraction 15 min after the 5-min period of ischemia, and Ca2+ deposits in these mitochondria were rapidly decreased. Plasma membrane Ca2+-ATPase activities were already significantly elevated before the 5 min of ischemia, and remained at a higher level subsequently compared to nonischemia-tolerant CA1 neurons. Changes in the mitochondrial Ca2+ distribution and Ca2+-ATPase activities in ischemia-tolerant CA1 neurons after the 5-min period of ischemia showed a strong resemblance to those in CA3 neurons, which originally possess resistance to such periods of ischemia. These findings suggest that enhanced or maintained activities of mitochondrial Ca2+ sequestration and plasma membrane Ca2+-ATPase reduced Ca2+ toxicity following 5-min ischemia in terms of time, resulting in escape from delayed neuronal death.
Perivascular Nerves of the Human Basal Cerebral Arteries: II. Changes in Aging and Alzheimer's Disease
Authors: Bleys Ronald L. A. W. , Cowen Tim , Groen Gerbrand J. , Hillen Berend
Published: November 2003

In the present study the intrinsic nerve plexuses of the basal cerebral arteries, derived from aged non-Alzheimer's and aged Alzheimer's disease patients were quantified and compared. A previous study described and quantified nerve density on similar arteries from healthy middle-aged patients. Whole-mount preparations of various segments of the basal cerebral arteries were stained for protein gene product 9.5. The deep nerve plexuses, located at the adventitial–medial border, were quantified by image analysis. Transverse cryostat sections were stained for various markers and quantified. Measurements on whole mounts demonstrated that nerve densities were highest in the posterior communicating artery and in the postcommunicating part of the posterior cerebral artery (PCA) for both aged and Alzheimer's groups. Statistical comparison showed a tendency toward decreased nerve density with aging, which was significant for the internal carotid artery, precommunicating part of the PCA, and the anterior choroidal artery in both non-Alzheimer's and Alzheimer's aged groups. In addition, in Alzheimer's patients nerve density was significantly lower in the precommunicating part of the anterior cerebral artery compared with the healthy aged group. Measurements on sections confirmed the tendency to decreased innervation with aging. It is concluded that densities of deep perivascular nerves of human basal cerebral arteries are subject to localized changes caused by aging and Alzheimer's disease.
Examination of Potential Mechanisms in the Enhancement of Cerebral Blood Flow by Hypoglycemia and Pharmacological Doses of Deoxyglucose
Authors: Horinaka Naoaki , Artz Nicole , Jehle Jane , Takahashi Shinichi , Kennedy Charles , Sokoloff Louis
Published: November 2003

Cerebral blood flow (CBF) rises when the glucose supply to the brain is limited by hypoglycemia or glucose metabolism is inhibited by pharmacological doses of 2-deoxyglucose (DG). The present studies in unanesthetized rats with insulin-induced hypoglycemia show that the increases in CBF, measured with the [14C]iodoantipyrine method, are relatively small until arterial plasma glucose levels fall to 2.5 to 3.0 m M, at which point CBF rises sharply. A direct effect of insulin on CBF was excluded; insulin administered under euglycemic conditions maintained by glucose injections had no effects on CBF. Insulin administration raised plasma lactate levels and decreased plasma K+ and HCO3– concentrations and arterial pH. These could not, however, be related to the increased CBF because insulin under euglycemic conditions had similar effects without affecting CBF; furthermore, the inhibition of brain glucose metabolism with pharmacological doses (200 mg/kg intravenously) of DG increased CBF, just like insulin hypoglycemia, without altering plasma lactate and K+ levels and arterial blood gas tensions and pH. Nitric oxide also does not appear to mediate the increases in CBF. Chronic blockade of nitric oxide synthase activity by twice daily i.p. injections of NG-nitro-L-arginine methyl ester for 4 days or acutely by a single i.v. injection raised arterial blood pressure and lowered CBF in normoglycemic, hypoglycemic, and DG-treated rats but did not significantly reduce the increases in CBF due to insulin-induced hypoglycemia (arterial plasma glucose levels, 2.5-3 m M) or pharmacological doses of deoxyglucose.
Neuroprotective Effect of NMDA Receptor Glycine Recognition Site Antagonism Persists When Brain Temperature is Controlled
Authors: Takaoka Seiji , Bart Robert D. , Pearlstein Robert , Brinkhous Ann , Warner David S.
Published: November 2003

Several lines of inquiry have indicated that glycine plays an important role in both glutamatergic neurotransmission and pathophysiology of cerebral ischemia. However, subacute outcome trials demonstrating the efficacy of glycine antagonists as neuroprotectants have not been performed with rigorous control of brain temperature. In this study, we investigated the effect of N-methyl-D-aspartate (NMDA) receptor glycine recognition site antagonism in a temperature-controlled rodent model of transient focal ischemia. Male Wistar rats underwent 75 min of intraluminal middle cerebral artery occlusion (MCAO). During MCAO and the first 24 h of reperfusion, rats (n = 10) were administered either vehicle or the glycine antagonist 5-nitro-6,7-dichloro-2,3-quinoxalinedione (ACEA 1021) i.v. as a bolus infusion of 5 mg/kg followed by 3.5 mg/kg/h (Low-Dose) or 10 mg/kg followed by 7 mg/kg/h (High-Dose) for 24 h. Cortical temperature was controlled at 38.0 ± 0.1°C during MCAO and the first 6 h of reperfusion. A 7-day recovery interval was allowed. Mean total infarct volume was reduced by ∼ 40% in both high- and low-dose groups ( p < 0.01). The preponderance of infarct reduction occurred in the cortex ( p < 0.01). Neurologic function correlated with the size of cerebral infarct ( p = 0.001). Neurologic grade was similarly improved by treatment with either dose ( p = 0.01). These results demonstrate that neuroprotection achieved by antagonism of the glycine recognition site persists when brain temperature is controlled, indicating a potent mechanism of action other than attenuating a hyperthermic response to ischemia.