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  • 1
    Electronic Resource
    Electronic Resource
    Site blocking effects in ethylidyne decomposition kinetics on ruthenium(001): in-situ study with infrared reflection absorption spectroscopy at elevated pressure (1993)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 12656-12659 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100151a002
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  • 2
    Electronic Resource
    Electronic Resource
    Transport des Hydroxyanalogons von Leucin in Bürstensaum-Membranvesikel des Kaninchendünndarms (1991)
    Springer
    European journal of nutrition 30 (1991), S. 233-237 
    Details
    ISSN: 1436-6215
    Keywords: Hydroxyanaloga von Aminosäuren ; H+-Ionen-stimulierter Transport ; Bürstensaum-Membranvesikel ; hydroxy analogues of amino acids ; proton driven transport ; brushborder membran vesicles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Hydroxy analogues of essential amino acids can be used in clinical nutrition to minimize nitrogen intake. In this study intestinal uptake of L-leucine hydroxy analogue into rabbit jejunal brush-border membrane vesicles was investigated. An inward directed H+-gradient was a driving force of uptake (pHoutside = 6.0; pHinside = 7.5) and led to a transient accumulation. The saturable system has a apparent transport constant Kt = 15.4 mM. By trans stimulation experiments it could be shown that both D- and L-stereoisomers of hydroxy analogues of branched chain amino acids as well as L-lactate share with the same H+-driven uptake system.
    Notes: Zusammenfassung Hydroxyanaloga essentieller Aminosäuren können ebenso wie ihre Ketoanaloga zur Minimierung der nutritiven Stickstoffaufnahme verwandt werden. In der vorliegenden Arbeit werden Mechanismen der intestinalen Absorption des L-Hydroxyanalogons von Leucin untersucht. Die Aufnahme dieses Substrates in Bürstensaum-Membranvesikel des jejunalen Kaninchendünndarms wird durch einen nach innen gerichteten Protonengradienten stimuliert (pHaußen 6,0; pHinnen 7,5). Die scheinbare Transportkonstante beträgt 15,4mM. Durch das carriervermittelte Transportsystem werden gleichfalls L- und D-Stereoisomere der anderen Hydroxyanaloga verzweigtkettiger Aminosäuren sowie L-Lactat aufgenommen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01610347
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  • 3
    Electronic Resource
    Electronic Resource
    In-situ FT-IRAS study of the CO oxidation reaction over Ru(001): III. Observation of a 2140 cm−1 C-O stretching vibration (1991)
    Springer
    Catalysis letters 10 (1991), S. 91-101 
    Details
    ISSN: 1572-879X
    Keywords: Ruthenium tricarbonyl ; CO oxidation on Ru(001) ; CO and oxygen coadsorption on Ru
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Utilizing Fourier Transform Reflection Absorption-Infrared Spectroscopy (FT-IRAS), we have investigated the CO oxidation reaction in-situ on a Ru(001) surface at high (≈ 10 Torr) pressures. Under certain temperature and reactant (CO and O2) partial pressure conditions, we observe for the first time on unsupported Ru a weakly adsorbed CO species which is characterized by an unusually high C-O stretching frequency of 2140 cm−1. A similar feature has been identified previously on small Ru particles in supported catalysts and attributed by some to a multicarbonyl species (−Ru(CO) n ,n 〉 1). By following the intensity of this feature on Ru(001) relative to other peaks in the spectra, we believe that the 2140 cm−1 peak observed here is most likely due to a highly perturbed linearly adsorbed monocarbonyl on partially oxidized Ru sites generated by locally high concentrations of coadsorbed oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00764740
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  • 4
    Electronic Resource
    Electronic Resource
    Hypertrophic obstructive cardiomyopathy as a manifestation of a cardiocutaneous syndrome (Noonan syndrome) (1991)
    Springer
    Journal of molecular medicine 69 (1991), S. 932-936 
    Details
    ISSN: 1432-1440
    Keywords: Noonan syndrome ; Turner phenotype ; Single gene mutation ; Atypical pulmonary stenosis ; Hypertrophic cardiomyopathy ; Cardiocutaneous syndrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The case of a 50-year-old patient with hypertrophic obstructive cardiomyopathy is reported. The patient demonstrated somatic signs of the Turner phenotype, but a cytogenetically normal karyotype was shown. These findings were compatible with the diagnosis of Noonan syndrome. The most commonly diagnosed cardiac disease in this syndrome is pulmonary stenosis, followed by hypertrophic cardiomyopathy. The patient's prognosis is limited by the natural history or the typical complications of the underlying cardiac lesion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01798545
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  • 5
    Electronic Resource
    Electronic Resource
    Alterations of ionic currents after reoxygenation in isolated cardiocytes of guinea-pigs (1991)
    Springer
    Pflügers Archiv 418 (1991), S. 238-247 
    Details
    ISSN: 1432-2013
    Keywords: Isolated cardiocytes ; Whole cell recording ; Reoxygenation ; Increased net current ; Transient inward current ; Ca current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Single myocytes were isolated from ventricles of adult guinea-pig hearts. The patch-clamp technique in the whole-cell configuration was used to study ionic currents. Experiments were performed in an experimental chamber that allowed the cells to be exposed to a sufficiently low O2 pressure to cause metabolic inhibition after 4–35 min (mean 14.1 min, n=20), which was indicated by the appearance of a large time-independent K current. Reoxygenation about 1 min after the first extra outward current was observed caused this current to vanish completely within 2–6 s if the calcium inside the pipette was buffered to negligible values with 20 mmol/l EGTA. With only 10 μM EGTA in the pipette, reoxygenation was followed by an arrhythmogenic period of 10–150 s duration, which was dominated by three types of event: (a) transient inward currents (I ti) developed during the first 5–10 s (26 cells); (b) the net current was increased by a factor of 1.9±0.4 (mean±SD, n=17) yielding a reversal potential for the increased component of −77±4 mV (mean±SD, n=4); and (c) the Ca current decreased by 20%–100% within the first 5–10 s. At the end of the arrhythmogenic period, I ti vanished, the net current recovered completely, and the Ca current recovered partially. At −45 mV, increasing preceding depolarization enlarged the amplitude of both the I ti and the net current, Iti being about four times more increased than the net current. The suppression of the Ca current was independent of the phase of the preceding I ti. We conclude that in isolated cardiocytes, after the induction of an anoxia-induced K current, reoxygenation causes a period of up to 150 s of cytosolic Ca overload, during which I ti is triggered, the net current is enhanced, and the Ca current is suppressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370522
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  • 6
    Electronic Resource
    Electronic Resource
    Reoxygenation-induced arrhythmogenic transient inward currents in isolated cells of the guinea-pig heart (1991)
    Springer
    Pflügers Archiv 418 (1991), S. 248-260 
    Details
    ISSN: 1432-2013
    Keywords: Isolated cardiocytes ; Transient inward current ; Current-voltage relationship ; Kinetics ; Na/Ca exchanger
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Transient inward currents (I ti), activated by a rise in intracellular Ca concentration, are believed to trigger cardiac arrhythmias in reperfused hearts. In this report, I ti in isolated cardiocytes from the guinea-pig were evoked by reoxygenation following a period of anoxia of between 4 min and 35 min. Reoxygenation was performed 1 min after the full development of an anoxia-induced time-independent K current. This current disappeared within 2–6 s and in the following 10 s I ti developed to maximum amplitude. I ti were evoked using a constant pulse pattern (holding potential V h=−45 mV; test potential V t=+10 mV; pulse duration 350 ms; frequency 1 Hz). In more than 95% of the cells, I ti at the holding potential I ti (−45 mV) declined with a time constant of τ=670±240 ms (mean±SD, n=17). In two cells, undamped oscillatory currents were observed. The amplitude of I ti (-45 mV) was proportional to the amplitude and duration of the preceding depolarizing test pulse. Test pulses of long duration (500 ms and 1000 ms, mean ± SD) to potentials positive to +10 mV produced slowly decaying tail currents (τ=391±51 ms, mean ± SD), which superimposed with I ti (−45 mV). The current/voltage relationship of I ti peaked between −30 mV and −10 mV and approximated zero at the most positive potentials, i.e. no reversal of I ti was found up to +80 mV. Using double-pulse protocols (prepulse potential +40 mV), I ti were enhanced at potentials negative to −30 mV and were also present in the range of the normal resting potential of ventricular heart cells. The instantaneous current-voltage relationship was monotone between −50 mV and +40 mV. Because of the dependence of I ti on the preceding depolarization, the instantaneous current-voltage relationship provides more reliable information on the voltage dependence of I ti. The interval between two subsequent I ti (−45 mV) values was 237±35 ms (mean ± SD, n=27) and depended on the amplitude of I ti (−45 mV) to increase by 5.2±0.5% (mean ± SD) per 100 pA decrease in I ti (−45 mV). A simple noise analysis showed that if one assumes that ionic channels are responsible for the generation of I ti (−45 mV), their unitary conductance cannot exceed 0.36 pS. We conclude that reoxygenation-induced I ti are triggered by a cyclic release of Ca from the sarcoplasmic reticulum and provide evidence that they are mediated by the electrogenic Na/Ca exchanger. The arrhythmogenic potency of reoxygenation-induced I ti is demonstrated under current-clamp conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370523
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  • 7
    Electronic Resource
    Electronic Resource
    Anoxia opens ATP regulated K channels in isolated heart cells of the guinea pig (1991)
    Springer
    Pflügers Archiv 419 (1991), S. 108-110 
    Details
    ISSN: 1432-2013
    Keywords: Isolated heart cells ; Anoxia ; ATP regulated potassium channels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied single channel ionic currents in cell-attached patches of guinea pig heart cells under conditions of anoxia (pO2〈0.1 torr) to identify the type of channels which contribute to the anoxia-induced time-independent K current in whole cells. In most experiments, K currents were recorded at negative potentials as inward currents with 150 mmol/l KCl in the pipette. After periods of 5–60 minutes of anoxia, opening events of one to four voltage-independent 83 pS channels developed whose open probability reached a steady state value between 0.6 and 0.95 (T=35°C). The reversal potential of the unitary currents, determined at 150 mmol/l and 10.8 mmol/l K+ in the pipette, showed that the channels were highly selective for K+ ions. Open time histograms were fitted by two or three exponentials of which the fast time constant (τo1=0.46±0.20 ms, mean±SD) was bandwidth-limited by our filter and the slow components substantially varied (τo2=1.5–19 ms: τo3=23–200 ms). Voltage ramp experiments showed that the channels were slightly rectifying in an inward direction. The unitary conductance of anoxia-induced outward currents at reduced K+ in the pipette was smaller (11 pS at 5.4 mmol K+, 25 pS at 10.8 mmol/l K+) than in excised patches. It is concluded that in isolated cardiocytes substrate-free anoxia causes opening of ATP regulated K channels whose conductance is reduced at physiological levels of [K+]o by a fast block, most likely by intracellular Mg++ and Na+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373754
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of anoxia on K and Ca currents in isolated guinea pig cardiocytes (1990)
    Springer
    Pflügers Archiv 416 (1990), S. 207-209 
    Details
    ISSN: 1432-2013
    Keywords: Isolated cardiocytes ; Anoxia ; AP shortening ; K current ; Ca current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Whole cell currents were measured in isolated cardiocytes of guinea pig under anoxic conditions (pO2 〈0.5 torr). After 2 to 32 (mean 11.2) minutes of anoxia, time independent outward currents developed gradually which had a linear current-voltage relation between -100 and +20 mV and reversed at the resting potential of the cells (-82 to -90 mV). After 20 to 170 (mean 38) seconds, the amplitude of these outward currents saturated (3.6±0.5 nA at +10 mV, n=23). Reoxygenation within one minute after the appearance of the first extra outward currents led in most cells (〉90%) to their complete disappearance in 2 to 4 (mean 2.87, n=15) seconds. Ca currents were not affected at the time when the first extra outward currents occurred. It is concluded that (i) the anoxia-induced outward current is carried by K+ ions probably through KATP channels which open at intracellular ATP concentrations below 1 mmol/l (Noma and Shibasaki 1985) and (ii) this degree of ATP depletion does not affect normal Ca channel function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370244
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