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  • 1
    Electronic Resource
    Electronic Resource
    Electrophysiological analysis of bicarbonate permeation across the peritubular cell membrane of rat kidney proximal tubule (1984)
    Springer
    Pflügers Archiv 401 (1984), S. 34-42 
    Details
    ISSN: 1432-2013
    Keywords: Basolateral HCO 3 − transport ; pH ; $$p_{{\text{CO}}_{\text{2}} } $$ ; Carbonic anhydrase ; Anion substitution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The membrane potential response of proximal tubular cells to changing HCO 3 − concentrations was measured in micro-puncture experiments on rat kidney in vivo. No significant effect was noticed when luminal bicarbonate concentration was changed. Changing peritubular HCO 3 − by substitution with Cl− resulted in conspicuous membrane potential transients, which reached peak values after 100–200 ms and decayed towards near control with time constants of ∼2s. The polarity of the potential changes and the dependence of the initial potential deflections on the logarithm of HCO 3 − concentration suggest a high conductance of the peritubular cell membrane for HCO 3 − buffer, but not for Cl−, SO 4 2− , or isethionate. At constant pH $$t_{{\text{HCO}}_{\text{3}}^ - } $$ was estimated to amount to ∼0.68. At constant $$p_{{\text{CO}}_{\text{2}} } $$ , $$t_{{\text{HCO}}_{\text{3}}^ - } $$ was even greater because of an additional effect of OH− or respectively H+ gradients across the cell membrane. The secondary repolarization may be explained by passive net movements of K+ and HCO 3 − across the peritubular cell membrane, which result in a readjustment of intracellular HCO 3 − to the altered peritubular HCO 3 − concentration. Application of carbonic anhydrase inhibitors in the tubular lumen reduced the initial potential response by one half and doubled the repolarization time constant. The same effect occurred instantaneously when the inhibitor was applied—together with the HCO 3 − concentration step—in the peritubular perfusate. This observation demonstrates that membrane bound carbonic anhydrase is somehow involved in passive rheogenic bicarbonate transfer across the peritubular cell membrane, and suggests that HCO 3 − permeation might occur in form of CO2 and OH− (or H+ in opposite direction).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581530
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Sperm tail entry into the mouse egg in vitro (1982)
    New York, NY : Wiley-Blackwell
    Gamete Research 6 (1982), S. 215-223 
    Details
    ISSN: 0148-7280
    Keywords: spermatozoon ; egg ; fertilization ; in vitro ; incorporation ; cincmatography ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Cumulus-free mouse eggs were placed on microscope slides and inseminated with capacitated mouse spermatozoa. Fertilization could then be observed through the phase contrast microscope and recorded by time-lapse cinematography. Following the penetration of the fertilizing spermatozoon through the zona pellucida and the fusion of the sperm head with the vitelline membrane, the entire sperm tail gradually entered the vitellus. The time required for tail incorporation into the vitellus as measured in 49 eggs varied from 3 h 3 min to 5 h 49 min, with a mean time of 4 h 23 min. When tail incorporation began, the greater part of the flagellum was still outside the zona pellucida; occasionally it slipped into the perivitelline space, but generally it remained outside the zona and shortened by degrees as incorporation proceeded. The motility of the fertilizing spermatozoon declined abruptly very soon after fusion of the sperm head with the vitellus and remained at a very low level during the 3-6 h required for tail incorporation. Sperm motility, therefore, does not appear to be the main determinant in tail incorporation and the primary mechanism responsible for it remains unclear. As the sperm tail slowly entered the vitellus, the second meiotic division was completed with concomitant extrusion of the second polar body. Key stages in second polar body formation were correlated with events in tail incorporation. Differences between fertilization in vitro and in vivo are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120060305
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  • 3
    Electronic Resource
    Electronic Resource
    Design of a magnetic field generator for experiments on magnetic effects in cell cultures (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 5 (1984), S. 399-410 
    Details
    ISSN: 0197-8462
    Keywords: magnet ; magnetic field ; tissue culture ; exposure system ; biological effects ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A magnetic field generator constructed of rare earth-cobalt magnets is proposed for examining the biological effects of static magnetic fields (less than 1 T) on tissue cultures. Important quantities of a magnetic field from a biological-effects viewpoint, ie, its strength and the product of strength and gradient, are analysed. A practical procedure for designing the generator with optimum parameters is given. Also, parameters are determined which will yield a sinusoidal spatial field distribution.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250050405
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    Paper (German National Licenses)
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