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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of isotope dilution mass spectrometry and graphite furnace atomic absorption spectrometry with Zeeman background correction for the determination of plasma selenium (1986)
    s.l. : American Chemical Society
    Analytical chemistry 58 (1986), S. 1272-1273 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00297a070
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  • 2
    Electronic Resource
    Electronic Resource
    Simultaneous multielement analysis of microliter quantities of serum for copper, iron, and zinc by graphite furnace atomic absorption spectrometry (1984)
    s.l. : American Chemical Society
    Analytical chemistry 56 (1984), S. 1651-1654 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00273a026
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of metals at the microgram-per-liter level in blood serum by simultaneous multielement atomic absorption spectrometry with graphite furnace atomization (1985)
    s.l. : American Chemical Society
    Analytical chemistry 57 (1985), S. 2-5 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00279a005
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  • 4
    Electronic Resource
    Electronic Resource
    Active and passive properties of rabbit descending colon: A microelectrode and nystatin study (1979)
    Springer
    The journal of membrane biology 45 (1979), S. 81-108 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The electrical properties of the basolateral membrane of rabbit descending colon were studied with microelectrode methods in conjunction with the polyene antibiotic nystatin. Two problems were examined: (i) the relative distribution of tight junctional, apical membrane and basolateral membrane resistances, and (ii) the ionic basis of the basolateral membrane potential. Intracellular K+ activity (K+) was measured using liquid ion exchanger microelectrodes ((K+)=76±2mm) and was found not to be in equilibrium with the basolateral membrane potential. In order to measure membrane resistances and to estimate the selective permeability of the basolateral membrane, the apical membrane was treated with nystatin and bathed with a K2SO4 Ringer's solution which was designed to mimic intracellular K+ composition. This procedure virtually eliminated the resistance and electromotive force of the apical membrane. Shunt resistance was calculated by two independent methods based on microelectrode and transepithelial measurements. Both methods produced similar results (R s =691±63 Ω cm2 and 770±247 Ω cm2, respectively). These findings indicate that the shunt has no significant selectivity, contrary to previous reports. Native apical membrane resistance was estimated as 705±123 V cm2 and basolateral membrane resistance was 95±14 V cm2. To estimate basolateral membrane selectivity, the serosa was bathed in a NaCl Ringer's solution followed by a series of changes in which all or part of the Na+ was replaced by equimolar amounts of K+. From measures of bi-ionic potentials and conductance during these replacements, we calculated potassium permeability and selectivity ratios for the nystatin-treated colon by fitting these results to the constant field equations. By correcting for shunt conductance, it was then possible to estimate the selective permeability of the basolateral membrane alone. Selectivity estimates were as follows:P Na/P K=.08 andP Cl/P K=.07 (uncorrected for shunt) andP Na/P K=.04 andP Cl/P K=.06 (basolateral membrane alone). In a second set of experiments, evidence for an electrogenic Na+ pump in the basolateral membrane is presented. A small ouabain-sensitive potential could be generated in the nystatin-treated colon in the absence of chemical or electrical gradients by mucosal, but not serosal, addition of NaCl. We conclude that this electrogenic pump may contribute to the basolateral membrane potential; however, the primary source of this potential is “passive”: specifically, a potassium gradient which is maintained by an “active” transport process. An appendix compares the results of nystatin experiments to amiloride experiments which were conducted separately on the same tissues. The purpose of this comparison was to develop a comprehensive model of colonic transport. The analysis reveals a leak conductance in the apical membrane and the presence of an amiloride-insensitive conductance pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869296
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  • 5
    Electronic Resource
    Electronic Resource
    On the effects of amphotericin B and ouabain on the electrical potentials ofNecturus gallbladder (1981)
    Springer
    The journal of membrane biology 60 (1981), S. 167-170 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Conclusion The experimental evidence against an electrogenic pump in theNecturus gallbladder is nonexistent because they are based upon insufficient knowledge about the true resistance of the serosal membrane: The data available are not incompatible with the existence of an electrogenic pump with a coupling ratio of 3∶2-if an ionic model of the cell behavior is used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870419
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  • 6
    Electronic Resource
    Electronic Resource
    Studies of sodium channels in rabbit urinary bladder by noise analysis (1984)
    Springer
    The journal of membrane biology 80 (1984), S. 135-151 
    Details
    ISSN: 1432-1424
    Keywords: Na+ channels ; channel turnover ; fluctuation analysis ; tight epithelium ; mammalian urinary bladder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Sodium channels in rabbit urinary bladder were studied by noise analysis. There are two components of short-circuit current (I sc) and correspondingly two components of apical Na+ entry, one amiloride-sensitive (termedI A and the A channel, respectively) and one amiloride-insensitive (I L and the leak pathway, respectively). The leak pathway gives rise tol/f noise, while the A channel in the presence of amiloride gives rise to Lorentzian noise. A two-state model of the A channel accounts well for how the corner frequency and plateau value of Lorentzian noise vary with amiloride concentration. The single-channel current is 0.64 pA, and the conducting channel density is on the order of 40 copies per cell. Triamterene blocks the A channel alone, and increasing external Na+ decreases the number but not the single-channel permeability of the A channel. Hydrostatic pressure pulses (“punching”) increase the number of both pathways. Repeated washing of the mucosal surface removes most of the leak pathway without affecting the A channel. Properties of the A channel revealed by noise analysis of various tight epithelia are compared, and the mechanism ofl/f noise is discussed. It is suggested that the A channel is synthesized intracellularly, stored in intracellular vesicles, transferred with or from vesicular membrane into apical membrane under the action of microfilaments, and degraded into the leak pathway, which is washed out into urine or destroyed. The A channel starts withP Na/P K∼30 and loses selectivity in stages untilP Na/P K reaches the free-solution mobility ratio (∼0.7) for the leak pathway. This turnover cycle functions as a mechanism of repair and regulation for Na+ channels, analogous to the repair and regulation of most intracellular proteins by turnover. Vesicular delivery of membrane channels may be operating in several other epithelia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868770
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  • 7
    Electronic Resource
    Electronic Resource
    Basolateral membrane potential of a tight epithelium: Ionic diffusion and electrogenic pumps (1978)
    Springer
    The journal of membrane biology 41 (1978), S. 117-148 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The contribution of specific ions to the conductance and potential of the basolateral membrane of the rabbit urinary bladder has been studied with both conventional and ion-specific microelectrode techniques. In addition, the possibility of an electrogenic active transport process located at the basolateral membrane was studied using the polyene antibiotic nystatin. The effect of ion-specific microelectrode impalement damage on intracellular ion activities was examined and a criterion set for acceptance or rejection of intracellular activity measurements. Using this criterion, we found (K+)=72mm and (Cl−)=15.8mm. Cl− but not K+ was in electrochemical equilibrium across the basolateral membrane. The selective permeability of the basolateral membrane was measured using microelectrodes, and the data analyzed using the Goldman, Hodgkin-Katz equation. The sodium to potassium permeability ratio (P Na/P K) was 0.044, and the chloride to potassium permeability ratio (P Cl/P K) was 1.17. Since K+ was not in electrochemical equilibrium, intracellular (K+) is maintained by active metabolic processes, and the basolateral membrane potential is a diffusion potential with K+ and Cl− the most permeable ions. After depolarizing the basolateral membrane with high serosal potassium bathing solutions and eliminating the apical membrane as a rate limiting step for ion movement using the polyene antibiotic nystatin, we found that the addition of equal aliquots of NaCl to both solutions caused the basolateral membrane potential to hyperpolarize by up to 20 mV (cell interior negative). This popential was reduced by 80% within 3 min of the addition of ouabain to the serosal solution. This hyperpolarization most probably represents a ouabain sensitive active transport process sensitive to intracellular Na+. An equivalent electrical circuit for Na+ transport across rabbit urinary bladder is derived, tested, and compared to previous results. This circuit is also used to predict the effects that microelectrode impalement damage will have on individual membrane potentials as well as time-dependent phenomena; e.g., effect of amiloride on apical and basolateral membrane potentials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01972629
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  • 8
    Electronic Resource
    Electronic Resource
    Electrical properties of the rabbit urinary bladder assessed using gramicidin D (1982)
    Springer
    The journal of membrane biology 67 (1982), S. 45-53 
    Details
    ISSN: 1432-1424
    Keywords: antibiotics ; gramicidin D ; tight epithelium ; membrane resistances ; electrogenic pump ; microelectrodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Recently, antibiotics have enjoyed widespread usage as tools in studies of epithelial transport. In the present study we assess the usefulness of the pore-forming antibiotic gramicidin D as a means for probing the electrical properties of the tight epithelium rabbit urinary bladder. Addition of 50 μM gramicidin to the mucosal bath (either a NaCl or KCl Ringer's solution) led to a large irreversible increase in the transepithelial conductance (G T ) within 800 sec.G T increased by approximately 1200% and 500% in KCl and NaCl Ringer's solutions, respectively. Microelectrode measurements of the resistance ration (the ration of apical membrane resitance to basolateral membrane resistance) showed that apical membrane resistance is dereased by the drug. Measurements of the basolateral membrane resistance (R bl ) and tight junctional resistance (R j ) using a new and independent method (based on the perturbation of basolateral membrane electrogenic Na+ pump) demonstrated thatR bl andR j were unaffected, suggesting that the effects of gramicidin are restricted to the apical membrane for periods of at least 2 hours after drug addition. The selectivity of the gramicidin-induced permeability in the apical membrane was calculated from measurements of the apical membrane potential after ion substitutions using a modified version of the constant field equation. The selectivity sequence for cations was Cs+〉K+〉Na+〉Li+〉choline. Unlike the commonly used polyene antibiotics nystatin and amphotericin B, gramicidin did not induce a significant Cl− permeability. In addition, the dose-response curve had a slope of 1. A method is described for calculating membrane resistances directly from transepithelial measurements under some conditions of gramicidin use, without requiring the use of microlectrode measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868646
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  • 9
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    Enhancement and Masking of Loudness by Environmental Factors: "Vegetation and Noise" (1987)
    Beverly Hills, Calif. : Periodicals Archive Online (PAO)
    Environment and behavior. 19:4 (1987:July) 411 
    Details
    ISSN: 0013-9165
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Psychology
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:f117-1987-019-04-000001
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  • 10
    Electronic Resource
    Electronic Resource
    Temporal and spatial variation in mercury concentrations in some albatrosses and petrels from the sub-Antarctic (1993)
    Springer
    Polar biology 13 (1993), S. 239-244 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mercury concentrations in albatrosses and some other large procellariiforms are very much higher than found in other groups of seabirds. Analysis of mercury concentrations in feather samples collected prior to 1950 and after this date showed slight, but significant, increases in three out of ten sub-Antarctic procellariiform species. The lack of widespread and pronounced increases in mercury concentrations in procellariiforms between these periods may indicate that industrial and agricultural emissions of mercury in the southern hemisphere have been relatively minor and the high concentrations are predominantly due to natural processes. Mercury concentrations were relatively consistent between body feathers of individuals, and showed no variation related to adult age (in years). Within species, mercury concentrations tended to be highest in New Zealand populations and lowest in Falkland Island and South Georgia populations. Mercury concentrations also varied among species, but not in a way that could be related to diet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238759
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