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  • 1
    Electronic Resource
    Electronic Resource
    Arachidonic acid and the control of body pattern inHydra (1993)
    Springer
    Development genes and evolution 202 (1993), S. 70-76 
    Details
    ISSN: 1432-041X
    Keywords: Arachidonic acid ; HETE ; Protein kinase C ; Lipoxygenase ; Hydra ; Coelenterates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Repeated stimulation ofHydra magnipapillata with the diacylglycerol (DG) 1,2-sn-dioctanoylglycerol (diC8) induces an increase in positional value and eventually the development of ectopic heads. Upon stimulation, the polyps release [14C]-arachidonic acid from previously labelled endogenous sources. Arachidonic acid (AA) is not released into the external medium but remains within the animal, AA, linoleic acid and their lipoxygenase products were identified by gas chromatography-mass spectrometry. Several metabolites were found, most abundantly 12-HETE (hydroxy-eicosa-tetraenoic acid), 8-HETE, 9-HODE (hydroxy-octadecadienoic acid), and 13-HODE; this is the first evidence of their presence in coelenterates. Externally applied AA causes ectopic head formation, though less effectively than diC8. When administered simultaneously, (diC8) and AA, which both are known to activate protein kinase C (PKC), act synergistically in inducing ectopic head formation. Since released endogenous AA can spread in tissues, it may mediate a temporal and spatial extension of PKC activation and, hence, broaden the range in which positional value increases. However, in addition to the activation of PKC, the generation of AA metabolites appears to be essential for the induction of ectopic head formation, since not only a selective inhibitor of PKC, chelerythrine, but also an inhibitor of lipoxygenases, NDGA (nordihydroguaiaretic acid), significantly reduces the effectiveness of both AA and DG.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00636531
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  • 2
    Electronic Resource
    Electronic Resource
    The haemodynamic effects and pharmacokinetics of intravenous nicorandil in healthy volunteers (1993)
    Springer
    European journal of clinical pharmacology 44 (1993), S. 27-33 
    Details
    ISSN: 1432-1041
    Keywords: Nicorandil ; vasodilator ; tolerance study ; blood pressure ; pharmacokinetics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the effects of intravenous nicorandil, a mixed arterial and venous vasodilator, in 48 healthy volunteers. Nicorandil (20, 28, 39, 54, 74, 103, 144, or 200 μg·kg−1) or placebo were given over 5 min to subjects supine (16 subjects, 2 doses) or sitting (32 subjects, 1 dose) in a single-blind crossover design. Electro-cardiographic intervals, blood pressure, and heart rate were measured before and for 8 h after dosing. Blood and urine safety laboratory studies were also performed before and after dosing. All intravenous infusions of nicorandil and placebo were well tolerated and there were no clinically important safety concerns. The most frequent adverse event after nicorandil was headache (24 events by 19 subjects), although its occurrence was not strictly dose related. One subject experienced transient symptomatic hypotension (144 μg·kg−1). Mean plasma nicorandil concentrations were dose-related and fell with a half-life of 0.7 to 1.2 h. Systemic clearance and volume of distribution tended to decrease as dose increased. Sitting subjects showed marginally lower (〈20%) systemic clearances and larger values of Cmax and AUC. Nicorandil produced dose-related reductions in blood pressure, with consistent statistically significant differences from placebo after the 144 and 200 μg·kg−1 doses. The falls in blood pressure were greater for diastolic pressure and in this supine position. At 200 μg·kg−1, the mean falls in systolic/diastolic pressures (mm Hg) during the first hour were 10.9/14.7 supine and 6.1/9.1 sitting; systolic pressure returned to baseline after 8 h and diastolic pressure after 4 h. Heart rate increased transiently (mean peak increase of 17–24 bpm at the end of the 144 and 200 μg·kg−1 infusions). Blood pressure and heart rate changes over time were statistically significantly correlated with plasma nicorandil concentrations. Individual areas under the blood pressure and heart rate change curves likewise correlated with plasma concentration curve areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315276
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  • 3
    Electronic Resource
    Electronic Resource
    The pharmacokinetics and haemodynamic effects of continuous nicorandil infusion in healthy volunteers (1993)
    Springer
    European journal of clinical pharmacology 45 (1993), S. 437-443 
    Details
    ISSN: 1432-1041
    Keywords: Nicorandil ; vasodilator ; continuous infusion ; blood pressure ; pharmacokinetics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the pharmacokinetics and haemodynamic effects of nicorandil after a 12-h infusion. Nicorandil is a mixed vasodilator combining the actions of a nitrate and a potassium channel opener. Nicorandil was infused for 12 h in 21 healthy volunteers at rates of 0.05, 0.10, and 0.20 μg·kg−1·min−1 using a placebo controlled, crossover design. Systemic blood pressure, heart rate, electrocardiographic (ECG) intervals, and cardiac output (impedance cardiography) were measured supine and standing. Dose-related, steady-state plasma nicorandil concentrations occurred within 3 to 4 h. Nicorandil's pharmacokinetics were linear with dose. Four 0.20 μg·kg−1·min−1 nicorandil infusions were terminated early primarily because of moderate or severe headaches. There were no safety concerns (ECG intervals, laboratory assays). Blood pressure fell versus placebo only in the standing position and heart rate increased slightly (not significant). That is, standing blood pressure in the 6 to 12 h interval fell from baseline 8.0*/6.8, 1.6/5.1, and 9.8*/7.9* mmHg (systolic/diastolic, *=P〈0.05 versus placebo) at 0.05, 0.10, and 0.20 μg·kg−1·min−1 respectively. Cardiac output increased slightly above placebo at lower doses. Haemodynamic changes correlated poorly with plasma nicorandil concentrations. Similar total doses were less well-tolerated when extended over 12 h. We saw no evidence of pharmacodynamic tolerance to nicorandil within 12 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315515
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  • 4
    Electronic Resource
    Electronic Resource
    Tailored elastic behavior of multilayers through controlled interface structure (1994)
    Springer
    Journal of computer-aided materials design 1 (1994), S. 111-148 
    Details
    ISSN: 1573-4900
    Keywords: Elastic behavior ; Atomistic computer simulation ; Interfaces ; Thin films ; Grain boundaries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Atomistic simulations are reviewed that elucidate the causes of the anomalous elastic behavior of thin films and composition-modulated superlattice materials. The investigation of free-standing thin films and of superlattices, composed of grain boundaries, shows that the elastic anomalies are not an electronic but a structural interface effect that is intricately connected with the local atomic disorder at the interfaces. The consequent predictions that (i)coherent strained-layer superlattices should show the smallest elastic anomalies and (ii) making the interfaces incoherent should enhance all anomalies, are validated by simulations of dissimilar-material superlattices. Such simulations can be an effective aid in tailoring the elastic behavior of composite materials because, in contrast with experiments, they allow one to systematically investigate simple, but well-characterized model systems with increasing complexity. This unique capability of simulations has enabled us to elucidate the underlying driving forces and, in particular, (i) to deconvolute the distinct effects due to the inhomogeneous atomic disorder, localized at the interfaces from the consequent interface-stress-induced anisotropic lattice-parameter changes and (ii) to separate the homogeneous effects of thermal disordering from the inhomogeneous effects due to the interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00708705
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  • 5
    Electronic Resource
    Electronic Resource
    Metamictization and U-PB isotopic discordance in single zircons: a combined Raman microprobe and SHRIMP ion probe study (1998)
    Springer
    Mineralogy and petrology 62 (1998), S. 1-27 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Wir präsentieren die Ergebnisse einer Untersuchung des Zussammenhangs von Metamiktisierung und U-Pb Isotopendiskordanz in Zirkonen mittles kombinierter SHRIMP-Ionenmikrosonden- und Ramanmikrosondenanalysen. Die räumliche Auflösung der verwendeten Analysensysteme, experimentell mit 200 μm3 (SHRIMP) und 80 μm3 (Ramansonde) bestimmt, gestattet den direkten Vergleich der in Mikrobereichen innerhalb von Zirkon-Einkristallen gemessenen Isotopendiskordanzen und Metamiktisierungsgrade. Wir zeigen, daß der während der SHRIMP-Analyse auf den Zirkon einwirkende Sauerstoffionenstrahl weder signifikante Amorphisierung noch Rekristallisation des benachbarten Zirkonmaterials im 1 μm-Bereich hervorruft. Es ist deshalb möglich, den Grad der Metamiktisierung eines Zirkon-Mikrobereiches auch in den SHRIMP-Analysengrübchen, d.h. erst nach dem Analysieren dieses Bereiches mit der Ionensonde, mittels hochauflösender Ramanmessungen unverfälscht zu bestimmen. Der Einsatz beider Mikromethoden liefert kombinierte Informationen zu den Gehalten und Verteilungen radioaktiver Elemente, zum Grad der Metamiktisierung und seiner Heterogenität und zur lateralen „Altersverteilung” innerhalb von Einzelkörnern. Wir weisen eine deutliche Korrelation des Grades der U-Pb-Isotopendiskordanz mit dem Grad der Metamiktisierung im Mikrobereich (15 μm Auflösung) nach. Dies stimmt mit früheren, an Einzelzirkonen und Populationen getätigten Beobachtungen überein, daß die Metamiktisierung von Zirkon dessen Potential zu sekundären Bleiverlusten erhöht.
    Notes: Summary We report results of a combined SHRIMP ion microprobe and Raman microprobe study of the correlation between metamictization and U-Pb isotopic discordance of zircon. The spatial resolution of the SHRIMP and Raman probe used are about 200 μm3 and 80 μm3, respectively. This allows a direct comparison of U-Pb isotopic discordance and metamictization of small areas within zircon crystals. We show that the impact of the oxygen ion beam on the zircon during the SHRIMP analysis does not cause significant amorphization or recrystallization in the remaining zircon on a scale of 1 μm. Consequently, it is possible to determine the initial degree of metamictization of zircon within and adjacent to a SHRIMP analytical spot by Raman microprobe measurements after performing SHRIMP analyses. A combination of the two microprobe techniques gives information on the concentration and distribution of radionuclides as well as the degree of metamictization and its heterogeneity and the lateral “age distribution” within the grain. We found that the degree of U-Pb isotopic discordance correlates closely with the degree of metamictization within single zircon grains, on a scale of 15 μm, which is consistent with previous results on the scale of single and multiple zircon grains showing that metamictization enhances the relative potential for secondary loss of radiogenic lead in zircon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01173760
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  • 6
    Electronic Resource
    Electronic Resource
    Information und Energie in der Physiologie (1966)
    Springer
    Helgoland marine research 14 (1966), S. 36-50 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung 1. Durch die Gleichberechtigung der Begriffe „Energie“ und „Information“ konnten in den letzten Jahrzehnten vor allem in der Sinnesphysiologie entscheidende Fortschritte dadurch erzielt werden, daß unter Verzicht auf die Untersuchung einzelner Energieprozesse zunächst der Informationsablauf im Gesamtfunktionssystem analysiert wurde. Dies wird am Beispiel der Optimalisierungsfunktion des Zentralnervensystems erläutert. 2. Die Adaptation der Sinneszelle stellt scheinbar einen Erregungsverlust, hinsichtlich der Informationsverarbeitung jedoch einen Gewinn dar. Letzterer besteht in der Anpassung eines Bereiches hoher Unterschiedsempfindlichkeit an die mittlere Reizstärke. Elektrophysiologische Untersuchungen am Sinnesorgansystem Ohr weisen auf die Mitbeteiligung und die große Bedeutung des Zusammenspiels mehrerer Stoffwechselvorgänge im Rahmen dieser Adaptation hin. 3. Komplizierte Stoffwechseleinflüsse sind auch bei zentralen Informationsverarbeitungsaufgaben, und zwar speziell bei der Drosselung aktiver Elemente im Zuge der Optimalisierungsfunktion, zu vermuten. 4. Die extreme Informationsreduktion im menschlichen Sensorium beruht auf selektiven Drosselungsvorgängen an hierarchisch tieferen Schichten des Sinnesorgan-systems, vor allem auch in Höhe der Hirnrinde. Sie wird durch rückläufige Faser-systeme bewirkt und ist objektivierbar.
    Notes: Abstract Research in sensory physiology proves the usefulness of describing distinct functions of sensory systems from the point of view of information processing, neglecting energetic (metabolic) processes, which may occur simultaneously. On the other hand, complex metabolic processes play an important role in sensory reception and sensory communication. Adaptation — in quite a few situations resulting in an actual gain of sensory information — is based upon interacting metabolic processes. It is conceivable that various enzyme systems, such as coenzyme B, involved in the building and destruction of a particular exitatory substance, e. g., acetylcholine and cholinesterase, influence the speed of these different metabolic processes within the sensory cells. It is even possible to separate the damage done to these processes by using an electrophysiological recording of combined action potentials on the auditory nerve and accounting for the time course of adaptation according toRanke's adaptation theory. The human central nervous system selects the 100 bit/sec processed for conscious perception from the 109 bit/sec offered from all sensory receptors in two principal ways: (1) “Specific auditory information” is modulated by “unspecific” information processed through the reticular formation of the brain stem; (2) descending fiber systems alter selectively the information flow on every level of the auditory pathway. The filtered information perceived, in turn triggers a set of inborn and learned behavioral responses, such as speech and motor reaction, altogether representing appromaximately 107 bit/sec. Metabolic processes possibly involved in this optimizing system are largely unknown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01611612
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  • 7
    Electronic Resource
    Electronic Resource
    Measurement of the turbulent flow field in a free-surface jet of water (1995)
    Springer
    Experiments in fluids 18 (1995), S. 397-408 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Measurements of the mean velocity and turbulence intensity are presented for a rectangular jet of water ejecting into a gaseous ambient. Data are reported for streamwise locations up to 30 nozzle widths from the discharge and spanwise locations covering the inner 80% of the jet width. The flow conditions at the nozzle discharge were controlled by using different nozzle designs (parallel-plate and converging) and flow manipulators (wire grid and screens). The results track the mean velocity and turbulence intensity profiles with streamwise distance, highlighting changes in both the profile shapes and magnitudes for both measured quantities. Independent of nozzle configuration, the mean velocity profile was shown to be most nonuniform and the turbulence intensity most nonhomogeneous at the nozzle discharge. With increasing streamwise distance, the mean velocity profile underwent a gradual transition to a completely uniform condition, while the turbulence field decayed and became homogeneous. The rate of viscous dissipation was shown to depend strongly on the nozzle exit condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208462
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  • 8
    Electronic Resource
    Electronic Resource
    Sample size and retention values in gradient liquid chromatography of synthetic polymers (1996)
    Springer
    Chromatographia 42 (1996), S. 185-190 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gradient elution of synthetic polymers ; Polystyrene and various styrene copolymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention times in gradient liquid chromatography of synthetic polymers are often dependent on sample size. They increase with column load if the separation mechanism is governed by a solution process but decrease with increasing load if the mechanism is governed by adsorption. Since retention times independent of sample size are a prerequisite for peak identification as well as for the correct measurement of elution bands of samples with a broad distribution, measures to counteract sample-size effects deserve attention. Usually both solubility and adsorption are effective in gradient liquid chromatography of synthetic polymers. An appropriate balance of both effects is suitable for diminishing the influence of sample size on retention time of synthetic polymers. Ternary gradients allowing independent control of solubility and adsorption are promising.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269651
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  • 9
    Electronic Resource
    Electronic Resource
    Control of adsorption and solubility in gradient high-performance liquid chromatography (1994)
    Springer
    Chromatographia 39 (1994), S. 557-563 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Copoly(styrene/methyl methacrylate) ; Gradient elution ; Precipitation chromatography of polymers ; Solubility of polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Copolymers from styrene and methyl methacrylate (MMA) were separated by both normal and reversedphase gradient chromatography. Both modes could be performed by sudden-transition gradients where the polymers were injected into a non-solvent whose polarity was either rather low (e.g.,n-heptane) or high (e.g., acetonitrile). Then the solvent strength of the starting eluent was rapidly increased to a given level by addition of dichloromethane. Under properly defined conditions, the sample components still remained on the column. Elution could be triggered off by the steady addition of another non-solvent whose polarity was opposite of that of the starting non-solvent. Thus, the mixture of five copolymers with MMA content ranging from 14 to 84% could be separated on a polar cyanopropyl column by injection inton-heptane and elution through acetonitrile (normal phase mode) and on a RP C18 column by injection into acetonitrile and elution throughn-heptane (reversed-phase mode), provided that in both modes about 30% dichloromethane was added to the starting non-solvent. The elution sequence in the reversed-phase mode was opposite to that in the normal-phase mode, obeying the approved polarity rules of chromatography in both cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268279
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  • 10
    Electronic Resource
    Electronic Resource
    Control of adsorption and solubility in gradient high performance liquid chromatography. Part 4. Sudden-transition gradient elution of styrene/ethyl methacrylate copolymers in reversed phase mode (1994)
    Springer
    Chromatographia 39 (1994), S. 170-174 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Copoly(styrene/ethyl methacrylate) ; Gradient elution ; Precipitation chromatography of polymers ; Solubility of polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Copolymers from styrene and ethyl methacrylate have been separated according to composition byn-heptane gradients on a C18 bonded phase after injection into acetonitrile and subsequent sudden transition to a concentration of either dichloromethane or tetrahydrofuran between 30 and 50% or 20 and 50%, respectively. Acetonitrile is a polar non-solvent for the copolymers under investigation and ensures proper retention of the samples on a non-polar stationary phase. Dichloromethane and tetrahydrofuran are good solvents of moderate polarity. The addition of, e.g., 30 vol% of one of these solvents increased the dissolution power of the starting eluent but not to the extent necessary for elution. The latter was achieved by the addition ofn-heptane, which is a non-solvent for the polymers investigated. Thus, its eluting power must be understood as the consequence of its modifying effect on the polarity of the eluent mixture. The higher the content of copolymer in ethyl methacrylate the earlier it was eluted. Since acetonitrile andn-heptane are only partly miscible, phase diagrams were measured after the addition of either tetrahydrofuran or dichloromethane as a third component. Homogeneous mixtures were obtained on addition of about 30% solvent (one of both of the latter).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274496
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