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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Discrete & computational geometry 22 (1999), S. 177-192 
    ISSN: 1432-0444
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. Aleksandrov [1] proved that a simple convex d -dimensional polytope, d ≥ 3 , is infinitesimally rigid if the volumes of its facets satisfy a certain assumption of stationarity. We extend this result by proving that this assumption can be replaced by a stationarity assumption on the k -dimensional volumes of the polytope's k -dimensional faces, where k ∈{1,. . .,d-1} .
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-055X
    Keywords: Schlüsselwörter Hämorrhagischer Schock ; Leukozytenadhäsion ; Lebermikrozirkulation ; Intravitalmikroskopie ; Key words Haemorrhagic shock ; Leukocyte adhesion ; Hepatic microcirculation ; Intravital microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Deferoxamine is known to reduce the iron-dependent generation of toxic oxygen- derived radicals during reperfusion of ischaemic tissue. The present study investigates the antioxidative properties of a deferoxamin-conjugated hydroxyethyl starch solution and its effects on the hepatic microcirculation in a haemorrhagic-shock rat model. Methods: Anaesthetized Sprague-Dawley rats were tracheotomized, prepared for invasive haemodynamic monitoring, and subject to haemorrhagic shock (MAP=40 mmHg during 60 min). The animals were resuscitated blood-free with lactated Ringer’s (RILA, n=10), gelatine (GELA, n=10), hydroxyethyl starch (HES, n=10), or deferoxamine-conjugated HES (DFO, n=8) solution (MAP≥70 mmHg). After 1 h of resuscitation the hepatic microcirculation was investigated by intravital microsscopy, the glutathione concentration was measured in liver homogenate, and the thiobarbituric acid reactive substances (TBARS) were determined as markers of lipid peroxidation. Results: Resuscitation resulted in restoration of MAP to ≥70 mmHg within a short time. The volume required to stabilise the arterial pressure during 1 h of resuscitation was significantly less in the DFO group compared with HES, GELA, and RILA. Significantly higher glutathione levels in liver homogenate as well as decreased TBARS levels were observed in the DFO group. The shock-induced increase of leukocyte adhesion in liver sinusoids was significantly attenuated by DFO. Conclusion: DFO significantly attenuates shock-induced oxidative stress, thereby reducing the early inflammatory reaction and improving the hepatic microcirculation.
    Notes: Zusammenfassung Fragestellung: Die Synthese der während der Reperfusion ischämischen Gewebes aus der Haber-Weiss-Reaktion Fe-abhängig hervorgehenden toxischen Sauerstoffradikale kann durch Deferoxamin, einen potenten Fe-Chelator, verringert werden. Die vorliegende Studie untersucht eine Deferoxamin-konjugierte Hydroxyethylstärkelösung auf ihre antioxidativen Eigenschaften und Auswirkungen auf die hepatische Mikrozirkulation am hämorrhagischen Schockmodell der Ratte. Methodik: Sprague-Dawley-Ratten wurden in Pentobarbitalanästhesie tracheotomiert, für ein invasives hämodynamisches Monitoring präpariert und einem hämorrhagischen Schock unterzogen (MAP=40 mm Hg während 60 min). Die blutfreie Volumentherapie wurde entweder mit Ringerlaktat (RILA; n=10), Gelatinelösung (GELA; n=10), Hydroxyethylstärke (HES; n=10) oder mit Deferoxamin-konjugierter Hydroxyethylstärkelösung (DFO; n=8) durchgeführt (MAP≥70 mm Hg). Eine Studie nach Beginn der Volumentherapie wurde die Mikrozirkulation der Leber intravitalmikroskopisch untersucht und die Glutathionkonzentration im Leberhomogenat sowie die Thiobarbitursäure-reaktiven Substanzen als Marker der Lipidperoxidation gemessen. Ergebnisse: Mit jeder der verwendeten Volumenersatzlösungen konnte der MAP innerhalb kurzer Zeit auf ≥70 mm Hg angehoben werden. In der mit DFO behandelten Gruppe konnte eine signifikant geringere Abnahme an reduziertem Glutathion im Lebergewebe sowie eine geringere Zunahme der Lipidperoxidation als Zeichen des verminderten oxidativen Stresses beobachtet werden. Die schockinduzierte verstärkte Leukozytenadhäsion in Lebersinusoiden wurde durch DFO signifikant vermindert. Schlußfolgerung: DFO vermindert signifikant den schockinduzierten oxidativen Streß, schwächt damit die frühe Entzündungsreaktion ab und bewirkt eine Verbesserung der Lebermikrozirkulation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-055X
    Keywords: Schlüsselwörter Schock ; Hämorrhagie ; Streßproteine ; Hitzeschockreaktion ; Hämoxygenase ; Key words Haemorrhage ; Shock ; Stress proteins ; Heat shock response ; Haeme oxygenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Objective: Recent evidence suggests a possible role for Haeme oxygenase (HO)-derived carbon monoxide (CO) in the regulation of vascular tone through elevation of cyclic 3′–5′ guanosine monophosphate (cGMP). Previous work from our laboratory has shown that blockade of the HO pathway by tin-protoporphyrin-IX (SnPP) after resuscitation from haemorrhage leads to a specific and profound increase in portal resistance while neither systemic nor hepatic arterial resistance are affected. We therefore investigated the organ-specific expression pattern of the stress-inducible protein haeme oxygenase-1/heat shock protein 32 after haemorrhage and resuscitation. Materials and methods: After approval of the protocol by the local review board, male Sprague-Dawley rats (n=6/group) were anaesthetised with pentobarbitone, instrumented for assessment of central haemodynamics, and subjected to haemorrhagic hypotension (40 mm Hg for 1 h) followed by resuscitation with 60% shed blood and Ringer’s solution or a time-matched sham protocol. Samples of liver, spleen, kidney, intestine, aorta, and lungs were harvested 5 h after the onset of resuscitation and subjected to Western-blot analysis using a specific anti-rat HO-1/hsp 32 antibody (StressGen, Sidney, Canada). Results: Resuscitation with shed blood/Ringer’s solution restored central haemodynamics and acid-base status while significant haemodilution was observed. Haemorrhage and resuscitation led to strong induction of HO-1 in the liver and slight induction in aortic tissue, while no increase in steady-state protein levels was observed in the other organs studied. Conclusion:These results suggest a specific contribution of the HO/CO pathway to maintenance of low hepatic portal resistance in vivo in a clinically relevant model of haemorrhagic shock and adequate resuscitation.
    Notes: Zusammenfassung Kohlenmonoxid (CO) entsteht als Intermediärstoffwechselprodukt im Hämabbau und kann nach neuesten Erkenntnissen ähnlich wie Stickstoffmonoxid über Aktivierung der Guanylatzyklase vasodilatorische Wirkungen entfalten. Für die endogene Bildung von CO ist ausschließlich die mikrosomale Hämoxygenase (HO) verantwortlich, die als konstitutives Enzym (HO-2) sowie in einer streßinduzierbaren Isoform (HO-1 oder Hitzeschockprotein 32) vorliegt. Hemmung des Hämstoffwechsels nach Schock und Volumentherapie führt nach eigenen Untersuchungen zu einer spezifischen Zunahme des Pfortaderwiderstands, ohne vasokonstriktorische Wirkungen in der systemischen Zirkulation hervorzurufen. In der vorliegenden Arbeit wurde daher das organspezifische Expressionsmuster der streßinduzierbaren Isoform des Enzyms nach hämorrhagischem Schock und Volumentherapie untersucht. Methoden und Ergebnisse: In einem kliniknah therapierten Schockmodell an der Ratte führte das Schockereignis zu einer geringfügigen Expression von HO-1 in Aortengewebe sowie zu einer ausgeprägten Expression in der Leber, während eine Induktion in anderen Organen wie Lunge, Darm oder Niere nach Hämorrhagie nicht nachweisbar war. Schlußfolgerung: Diese Ergebnisse legen nahe, daß HO-1/Hitzeschockprotein 32 in der Leber ein streßinduzierbares Vasodilatatorsystem, das zur Aufrechterhaltung der Leberperfusion nach hämorrhagischem Schock beiträgt, darstellt.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 74 (1996), S. 51-58 
    ISSN: 1432-1440
    Keywords: Key words Tumor necrosis factor ; Hemorrhagic shock ; Leukocyte adhesion ; Intravital microscopy ; Liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The relevance of tumor necrosis factor-α (TNF-α) inducing early inflammatory reactions in the liver after hemorrhagic shock, for example, leukocyte adhesion, has been well described. This study evaluated the anti-inflammatory effects of a monoclonal antibody against TNF-α (TN3.19.12) in terms of the time of application, namely, prior to shock induction, at the time of resuscitation, and after resuscitation. The hepatic microcirculation was investigated by intravital fluorescence microscopy in female Sprague-Dawley rats undergoing severe hemorrhagic shock for 60 min and subsequent resuscitation. TN3.19.12 or placebo was given in a randomized and blinded manner either 60 min prior to shock induction, 1 min prior to resuscitation, or 15 min after the onset of resuscitation. The number of firmly adherent leukocytes in the livers of treated animals depended on the time of application of TN3.19.12. Leukocyte adhesion was significantly reduced when TN3.19.12 was given prior to shock induction or at the time of resuscitation and was less effective when administered after the onset of resuscitation. The results further confirm that TNF-α initiates very early pathological leukocyte adhesion in the liver 5 h following shock. Inhibition of leukocyte adhesion after shock, however, depends strongly on the time of TNF-α blocking. While TN3.19.12 prior to shock induction resulted in most effective attenuation, only very early treatment allowed limitation of posttraumatically increased leukocyte adhesion.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-072X
    Keywords: Key words Phototaxis ; R-bodies ; Cysts ; Swarming ; motility ; Photopigment synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rhodospirillum centenum exhibited a number of general properties typically observed in nonsulfur purple bacteria, but also displayed a number of unusual characteristics that include: (1) conversion of the vibrioid/spiral cells to thick-walled cysts under certain growth conditions; (2) absence of O2 repression of photopigment synthesis; (3) synthesis of “R-bodies”; and (4) swarming motility on agar surfaces that allows macroscopic observation of colony phototaxis. The unusual characteristics indicate that Rsp.centenum will prove to be a valuable experimental system for investigating various basic problems, especially in connection with photosensory phenomena and the regulation of photopigment synthesis by dioxygen and light. The present comparative study of 13 strains was undertaken to further define the Rsp. centenum biotype.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-072X
    Keywords: Key wordsRhodospirillum centenum ; Phototaxis ; Swarm colonies ; Action spectrum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Most photosynthetic microorganisms have the capability of photosensing light quality and intensity. Movement of motile photosynthetic microorganisms to locales that offer optimal physical and chemical conditions for light-dependent growth provides obvious selective advantages. Among phototrophs, many cyanobacteria and algae migrate towards or away from the direction of light, a process termed phototaxis. In contrast, anoxygenic photosynthetic bacteria are believed to respond to changes in light intensity in a manner that is not related to the direction of light, a process that is often described by the term "photophobic". We recently reported that "swarm colonies" of the purple photosynthetic bacterium Rhodospirillum centenum are capable of macroscopically visible phototactic behavior. In the present study we further characterize the phototactic behavior of R. centenum swarm colonies and provide an action spectrum that delineates regions of the spectrum that elicit positive and negative phototaxis.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3833-3838 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Groove profiles are computed under isotropic conditions for the intersection of a periodic array of grain boundaries with an external surface, assuming that grain boundary flux I is directed to (I(approximately-greater-than)0) or away from (I〈0) the surface. When I=0, the surface assumes an equilibrium (time-independent) profile. For I≠0, in a range bounded by upper and lower limits that depend on geometry and material parameters, a global steady-state develops in which the entire surface advances (I(approximately-greater-than)0) or recedes (I〈0) from its original position at constant velocity. Beyond these limits, the surface near the groove roots becomes diffusively detached from the remaining surface. A rapidly growing ridge (I(approximately-greater-than)0) or slit (I〈0) then develops along each grain boundary, whose tip ultimately translates at constant velocity in a local steady state, leaving the remaining surface behind. These velocity regimes govern the ultimate stability of polycrystalline materials subjected to large electric (electromigration) or stress (creep) fields, especially in thin films where grain size approximates film thickness. © 1995 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6670-6676 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Advancement of a fine slit along a planar grain boundary in an electric field E0, applied parallel to the slit, is investigated by considering electromigration along both the grain boundary and the slit surface. Electrically induced flux in the grain boundary Igb (+ toward the slit tip) and both electrically and curvature-induced fluxes on the slit surfaces are considered assuming 2Is〉Igb, where Is is the flux (+ away from the slit tip) on each of the parallel slit surfaces far removed from the tip. Steady-state solutions of the transport equations are classified according to the value of a parameter β=tan−1 (2Is/Igb) which, under reasonable assumptions, depends on material parameters only. For 5π/4≥β≥β2, unique steady-state solutions exist; for β2〉β〉β1, multiple steady-state solutions occur; below β1≥π/4, no steady-state solution is possible. Since β1〈π/2, Igb〉0 (flux exiting the grain boundary into the slit) for all cases in which no steady-state solution is possible. In the case of multiple solutions, those corresponding to smallest width (and hence largest velocity) are determined. For all steady-state solutions, slit width and tip velocity scale as E−1/20 and E3/20, respectively. Results also apply to the propagation of a slit within a grain or along a passivation layer. Generally, tip velocities can approach 1 nm/s (3.6 μm/h), thereby representing a likely failure mechanism in fine-line (near bamboo structure) interconnects. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 194-196 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Previous treatments of void shape evolution during electromigration have been restricted to nonsingular void surfaces. We consider the lateral spreading of a void when its leading surface is a singular facet. The facet may nucleate at the leading surface of a void migrating within one grain or may develop when a singular surface is exposed by impingement of the void at a (transverse) grain boundary. Advance of the facet requires a source of steps that we assume to be absent; void spreading results. A stationary void shape is possible when a dimensionless parameter is less than a critical value (estimated), whereas above this value the void spreads indefinitely. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: For screening atopy risk in 6401 (84%) of all infants born during the year 1990 in six obstetric departments of five German cities, cord-blood IgE values were determined with CAP-RAST-FEIA. After cases with elevated IgA values had been excluded, 25 % of the values were above the detection limit of 0.35 kU/1, and 8.5% were above 0.9 kU/1. Boys had significantly higher values than girls (P≤0.001). The distribution of values was significantly different for different nationalities of mothers (P≤0.001). The percentage of elevated values (≥0.9kU/l) increased significantly with the number of close family members with atopic history (P≤0.001). Regarding the atopic history of the father, siblings, and mother separately, only the mother's history had a significant association with the cord-blood IgE class (P≤0.001). The IgE values of 81 twin pairs correlated significantly with a coefficient of r = 0.4909 (P≤0.001). The smoking history of the parents during pregnancy showed an association with cord-blood IgE values (P≤0.02). No significant association could be shown between cord-blood IgE distribution and other variables, i.e., gestational age, birth size, birth modus, Apgar score, cord-blood pH value, neonatal problems, parity, age of the mother, medication during pregnancy, educational level of mother or father, time of year, or obstetric department. It is hypothesized that, in addition to some postpartum contamination or placental transfer of maternal IgE, cord-blood IgE values are also determined by the fetal immunologic reaction to intrauterine exposure to allergens and trigger factors, and by genetic influences.
    Type of Medium: Electronic Resource
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