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  • 1
    Electronic Resource
    Electronic Resource
    The magnetic field of an isolated neutron star from X-ray cyclotron absorption lines (2003)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 423 (2003), S. 725-727 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Isolated neutron stars are highly magnetized, fast-rotating objects that form as an end point of stellar evolution. They are directly observable in X-ray emission, because of their high surface temperatures. Features in their X-ray spectra could in principle reveal the presence of atmospheres, ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature01703
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  • 2
    Electronic Resource
    Electronic Resource
    INVOLVEMENT OF α1-ADRENOCEPTORS IN CHRONOTROPIC RESPONSES TO ENDOGENOUSLY RELEASED AMINES IN THE PITHED RAT (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 15 (1988), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. In pithed rats, yohimbine (1 mg/kg i.v.) enhanced the positive chronotropic responses to spinal stimulation of cardiac sympathetic nerves with eight pulses delivered at 2 or 4 Hz, indicating that auto-inhibition was operating, but did not increase responses to shorter lengths of trains of 8 pulses at 8, 16 or 32 Hz which did not allow sufficient time for auto-inhibition to come into effect.2. The positive chronotropic response to cardiac sympathetic nerve stimulation with eight pulses at 8 Hz of about 60 beats/min was not affected by prazosin (1 mg/kg) or diltiazem (0.2 mg/kg), but was reduced to about 20% of the control value by propranolol (1 mg/kg).3. In the presence of propranolol, the residual positive chronotropic responses to cardiac sympathetic nerve stimulation were virtually abolished by prazosin (1 mg/kg) or diltiazem (0.2 mg/kg).4. The positive chronotropic response to tyramine (0.1 mg/kg i.v.) was reduced from 100 to 12 beats/min by propranolol (1 mg/kg), and the residual response was abolished by prazosin.5. The findings indicate that noradrenaline released from cardiac sympathetic terminals by nerve stimulation or by tyramine acts on α1-adrenoceptors to produce a positive chronotropic response that is revealed when β-adrenoceptors are blocked.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1988.tb01006.x
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  • 3
    Electronic Resource
    Electronic Resource
    Stereoselective effects of mexiletine enantiomers on sodium currents and excitability characteristics of adult skeletal muscle fibers (1995)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 352 (1995), S. 653-661 
    Details
    ISSN: 1432-1912
    Keywords: Key words Sodium channel ; Excitability ; Skeletal muscle ; Enantiomers ; Mexiletine ; Tocainide ; Use-dependent block ; Myotonia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The effects of the enantiomers of mexiletine were tested on sodium currents of frog skeletal muscle fibers recorded by means of the three vaseline gap voltage clamp method and compared with the effects produced by tocainide enantiomers. The R-(−) mexiletine produced a tonic block of the sodium current, elicited by single depolarizing test pulses from the holding potential of −100 mV to −20 mV, with an IC50 of 43.9±1 μM, whereas the corresponding S-(+) enantiomer produced the same effects at about twofold higher concentrations. A similar stereoselectivity was observed with tocainide enantiomers, but at about 5 fold higher concentrations. Both the R-(−) and S-(+) enantiomers of mexiletine and tocainide produced a further use-dependent block of sodium currents when the test pulse was applied repetitively at a frequency of 2 Hz. The use dependent behaviour led to a significant lowering of the IC50 values with respect to the tonic block but the eudismic ratios ([IC50S-(+)]/[IC50R(−)]) and the relative potency between mexiletine and tocainide were maintained. All the tested compounds produced a left shift of the steady state inactivation curves (h∞) , suggesting a high-affinity interaction with the inactivated sodium channels. Again a stronger potency of R-(−) vs. S-(+) enantiomers and of mexiletine vs. tocainide was observed. The excitability characteristics recorded from the semitendinosus muscle by the two microelectrode technique were modified by the tested drugs in agreement with their ability to block sodium current. Thus a concentration-related increase in the threshold current required to elicit an action potential was observed along with a decrease in the amplitude and a shortening of the latency of action potential and a decrease in the firing capability of the membrane. Again the R-(−) isomers were more potent than the S-(+) ones and mexiletine was more effective than tocainide. These data corroborate the presence of a stereospecific site for these drugs on adult skeletal muscle sodium channels. The constant eudismic ratios between the enantiomers during both tonic and use-dependent block suggest that the increase in the apparent affinity of the receptor during state-dependent conformational changes of the channel does not enhance its stereospecificity. The decrease in effective concentration upon high frequency stimulation supports the potential usefulness of low doses of R-(−) mexiletine in the treatment of the abnormal hyperexcitability of the myotonic muscles, with a likely reduction of unwanted side effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00171325
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  • 4
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    Unknown
    Aggregation in Sraffa's Simple Production Model (1987)
    Wien : Periodicals Archive Online (PAO)
    Journal of economics/Zeitschrift für Nazionalökonomie. 47 (1987) 167 
    Details
    ISSN: 0931-8658
    Topics: Economics
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:4223-1987-047-00-000002
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of taurine analogues on chloride channel conductance of rat skeletal muscle fibers: a structure-activity relationship investigation (1994)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 349 (1994), S. 416-421 
    Details
    ISSN: 1432-1912
    Keywords: Key words: Skeletal muscle – Chloride channel conductance – Taurine binding site – Taurine analogues – Structure-activity relationship
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. In rat skeletal muscle, taurine was proposed to interact with a low affinity binding site on sarcolemmal phospholipids near chloride channel, increasing chloride conductance (GCl). In an attempt to evaluate the structure-activity relationship between taurine and its binding site, a series of N-azacycloalkenyl analogues of taurine (A: N-(1′aza-cyclohepten-2′yl)-2-aminoethane sulfonic acid; B: N-(1′-aza-cyclopenten-2′-yl)-2-aminoethane sulfonic acid; C: N-(1′aza-cyclohepten-2′-yl)-3-aminopropane sulfonic acid; D: N-(1′aza-cyclopenten-2′-yl)-3-aminopropane sulfonic acid) have been synthetized and tested in vitro on rat extensor digitorum longus (EDL) muscle. In spite of the presence of a bulky and lipophilic 5 or 7 membered heterocycle linked to the taurine amino group, analogues A and B determined an increase of GCl, although less potently than taurine. Also 3-aminopropane sulfonic acid (homotaurine), tested in comparison, showed less activity in increasing GCl with respect to taurine, probably for the increased distance between charged groups. Taurine analogues C and D, which differ from compounds A and B for an additional methylene group, showed much lower activity in increasing GCl. It has been reported that guanidinoethane sulfonate (GES) displaces taurine from the low affinity site on sarcolemma by only 7%. This compound, characterized by lower charge density on the guanidinium cationic head, applied in vitro on EDL muscle, show reduced taurine-like activity in increasing GCl. Our results support the hypothesis that the effect of taurine on muscle GCl is due to a specific binding on a low affinity site on sarcolemma and that charge delocalization reduces the binding probability more than the substitution of the primary amino group or the increased distance between charged groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00170889
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