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  • 1
    Electronic Resource
    Electronic Resource
    Erratum (1999)
    Springer
    Annales geophysicae 17 (1999), S. 437-437 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-999-0437-2
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  • 2
    Electronic Resource
    Electronic Resource
    Calcium fluxes in internally dialyzed giant barnacle muscle fibers (1975)
    Springer
    The journal of membrane biology 23 (1975), S. 157-179 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Calcium-45 fluxes have been examined in isolated giant barnacle muscle fibers subjected to internal solute control by means of “internal dialysis”. The45Ca efflux was dependent upon the concentrations of both total and ionized internal Ca (Ca2+ buffered with EGTA). With a total Ca concentration of 2.0mm and a 1∶2 Ca/EGTA ratio (nominal [Ca2+] i =0.13 μm), the Ca efflux averaged 1.2 pmoles/cm2 sec. Under identical conditions, the mean Ca influx was only 0.36 pmoles/cm2 sec. The large Ca efflux may not be attributed to leak of the CaEGTA complex, since a 2.5-fold increase in the EGTA concentration (nominal [Ca2+] i =0.032 μm)reduced the45Ca efflux by one-third. Furthermore, when EDTA was used to buffer the internal Ca concentration (in the absence of internal Mg), the steady efflux of14C-EDTA was only about 10% of the45Ca efflux (in parallel experiments). The time-course of the45Ca fluxes also appeared anomalous in that45Ca influx reached a steady level much more rapidly than45Ca efflux in fibers of comparable diameters. If the muscle fibers are treated as right circular cylinders, these data imply that the apparent diffusion coefficient for inwardly-moving Ca is much larger than for outwardly-moving Ca. In contrast to Ca efflux, the outward diffusion of22Na,14C-EDTA and3H2O appears to be limited primarily by the permeability of the dialysis tube wall. Some, but not all, of the anomalous behavior of the Ca fluxes can be reconciled if the deep, branched infoldings of the barnacle muscle surface membrane are taken into account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870249
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  • 3
    Electronic Resource
    Electronic Resource
    Ionic permeabilities of anAplysia giant neuron (1975)
    Springer
    The journal of membrane biology 21 (1975), S. 353-374 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary In a giant neuron ofAplysia californica, permeabilities and conductances obtained by measuring net fluxes of Na+, K+ and Cl− with ion-specific microelectrodes were compared with those obtained by measuring transmembrane current and potential changes when the three ions were varied in the external solution. Net fluxes were measured with ion-specific microelectrodes, after blocking metabolic processes, thus allowing movement of ions down their electrochemical gradients. Permeabilities and conductances obtained from the “chemical” measurements (i.e., ion-specific electrodes) were generally comparable to the values obtained from “electrical” measurements. Where discrepancies occurred, they could be explained by showing that some of the assumptions necessary to use the “electrical” method were not quantitatively true in this system. The absolute magnitudes of the permeabilities are significantly less than those found in many axonal preparations. There is also a relatively highP Na/P K ratio. The selectivity of the membraneagainst ions such as Tris+ and MeSO 3 − is not good, Tris+ being nearly as permeable as Na+ and MeSO 3 − about one-half as permeable as Cl−. These properties may be characteristic of somal membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01941076
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  • 4
    Electronic Resource
    Electronic Resource
    Sodium-calcium exchange and calcium-calcium exchange in internally dialyzed squid giant axons (1975)
    Springer
    The journal of membrane biology 22 (1975), S. 285-312 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The influx and efflux of calcium (as45Ca) and influx of sodium (as24Na) were studied in internally dialyzed squid giant axons. The axons were poisoned with cyanide and ATP was omitted from the dialysis fluid. The internal ionized Ca2+ concentration ([Ca2+] i ) was controlled with Ca-EGTA buffers. With [Ca2+] i 〉0.5 μm,45Ca efflux was largely dependent upon external Na and Ca. The Na 0 -dependent Ca efflux into Ca-free media appeared to saturate as [Ca2+] i was increased to 160 μm; the half-saturation concentration was about 8 μm Ca2+. In two experiments24Na influx was measured; when [Ca2+] i was decreased from 160 μm to less than 0.5 μm, Na influx declined by about 5 pmoles/cm2 sec. The Na 0 -dependent Ca efflux averaged 1.6 pmoles/cm2 sec in axons with a [Ca2+] i of 160 μm, and was negligible in axons with a [Ca2+] i of less than 0.5 μm. Taken together, the Na influx and Ca efflux data may indicate that the fluxes are coupled with a stoichiometry of about 3 Na+-to-1 Ca2+. Ca efflux into Na-free media required the presence of both Ca and an alkali metal ion (but not Cs) in the external medium. Ca influx from Li-containing media was greatly reduced when [Ca2+] i was decreased from 160 to 0.23 μm, or when external Li was replaced by choline. These data provide evidence for a Ca−Ca exchange mechanism which is activated by certain alkali metal ions. The observations are consistent with a mobile carrier mechanism which can exchange Ca2+ ions from the axoplasm for either 3 Na+ ions, or one Ca2+ and an alkali metal ion (but not Cs) from the external medium. This mechanism may utilize energy from the Na electrochemical gradient to help extrude Ca against an electrochemical gradient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868176
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  • 5
    Electronic Resource
    Electronic Resource
    Chemical ozone loss in the Arctic vortex in the winter 1995–96: HALOE measurements in conjunction with other observations (1998)
    Springer
    Annales geophysicae 17 (1998), S. 101-114 
    Details
    ISSN: 0992-7689
    Keywords: Chemical ozone loss (Arctic vortex 1995–96; halogen chemistry)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Severe chemical ozone loss has been detected in the Arctic in the winter and spring of 1995–96 by a variety of methods. Extreme reductions in column ozone due to halogen catalysed chemistry were derived from measurements of the Halogen Occultation Experiment (HALOE) on board the Upper Atmosphere Research Satellite in the Arctic vortex. Here, we discuss further aspects of the HALOE observations in the Arctic over this period. Potential problems, both in the data themselves and in the methodology of the data analysis are considered and the reason for the differences between the Arctic ozone losses deduced from HALOE data version 17 and 18 is analysed. Moreover, it is shown that HALOE measurements in the Arctic in winter and spring 1995–96 compare well with observations by other ground-based and satellite instruments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-999-0101-x
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  • 6
    Electronic Resource
    Electronic Resource
    Experiences with the national citation reports database for measuring national performance: The case of Mexico (1996)
    Springer
    Scientometrics 35 (1996), S. 247-255 
    Details
    ISSN: 1588-2861
    Source: Springer Online Journal Archives 1860-2000
    Topics: Information Science and Librarianship , Nature of Science, Research, Systems of Higher Education, Museum Science
    Notes: Abstract The National Citation Report (NCR) is an integrated citation file supplied by the Institute for Scientific Information (ISI), of an individual country's articles in science and social sciences. Our experience with the NCR database for Mexico suggests that this is an important addition to the tools available for carrying out bibliometric analysis of research performance. However, in order to generate reliable and accurate indicators using these datafiles we recommend that these be handled by specialists well acquainted with the ISI information products and with the scientific setup of the country concerned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02018482
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  • 7
    Electronic Resource
    Electronic Resource
    p H-sensitive activation of the intracellular- p H regulation system in squid axons by ATP- γ -S (1988)
    [s.l.] : Nature Publishing Group
    Nature 332 (1988), S. 262-265 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The experiments were performed on single squid giant axons. The intracellular milieu was controlled by internal dialysis16, and /?Hi was monitored with a pH-sensitive glass microelec-trode17'18. Because acid-extruding transporters such as the Na-dependent C1-HCO3 exchanger are inactive at ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/332262a0
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  • 8
    Electronic Resource
    Electronic Resource
    The effects of tropical cirrus clouds on the abundance of lower stratospheric ozone (1996)
    Springer
    Journal of atmospheric chemistry 23 (1996), S. 209-220 
    Details
    ISSN: 1573-0662
    Keywords: cirrus clouds ; heating rates ; tropics ; lower stratospheric ozone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The distribution of many chemical constituents of the atmosphere (e.g., ozone) is at least partially determined by the distribution of net radiative heating in the atmosphere. In this paper, we demonstrate the significant effect of high cirrus clouds on the net radiative heating of the tropical lower stratosphere. A model of tropical lower stratospheric ozone is then used to demonstrate the sensitivity of calculated ozone to the varying cloud cover used in the model. We conclude that calculated ozone is sensitive to the inclusion of clouds in models and that models of the atmosphere should include a realistic description of tropical cirrus clouds in order to accurately simulate the chemical composition of the atmosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00048261
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  • 9
    Electronic Resource
    Electronic Resource
    Calcium efflux from internally dialyzed squid axons: The influence of external and internal cations (1974)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 2 (1974), S. 558-581 
    Details
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Internal dialysis techniques have been used to examine the influence of external and internal cations on Ca efflux from ATP-depleted squid axons. The main observation is that Ca efflux is promoted by external Na and inhibited by internal Na. The Na0 -dependent Ca efflux appears to be a function of [Na]03, and is also affected by the membrane potential; a 25 mV depolarization may cause as much as an e-fold decrease in Ca efflux. These data are consistent with a counter-transport exchange of 3Na+-for-1Ca2+. A Ca0-dependent Ca efflux has also been observed; it is prominent in Na sea water or Le sea water, and is markedly diminished in choline sea water. This flux is consistent with the idea of a Ca-Ca exchange diffusion process. Taken together, the Na0 - and the Ca0 -dependent Ca effluxes fit a two-site model for carrier-mediated Ca transport; one site binds two Na+ or one Ca2+, while the second site can bind either one Na+ or one Li+. The data reported here suggest that both sites must be filled on the inward journey, but that only the Ca-binding site need be occupied on the outward journey of the carrier. A mechanism of this type could derive sufficient energy from the Na and voltage gradients to maintain a [Ca2+]0/[Ca2+]i concentration ratio of about 104 in the absence of ATP. The present experiments do not, however, rule out the possible participation of a metabolically driven Ca transport mechanism in vivo.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400020505
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