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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 174 (2000), S. 167-179 
    ISSN: 1432-1424
    Keywords: Key words: BK channel — Nonselective cation channel — Cation absorption — Inner ear epithelium — Patch clamp — Vibrating probe — Gerbil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. The outer sulcus epithelium was recently shown to absorb cations from the lumen of the gerbil cochlea. Patch clamp recordings of excised apical membrane were made to investigate ion channels that participate in this reabsorptive flux. Three types of channel were observed: (i) a nonselective cation (NSC) channel, (ii) a BK (large conductance, maxi K or K Ca ) channel and (iii) a small K+ channel which could not be fully characterized. The NSC channel found in excised insideout patch recordings displayed a linear current-voltage (I-V) relationship (27 pS) and was equally conductive for Na+ and K+, but not permeable to Cl− or N-methyl-d-glucamine. Channel activity required the presence of Ca2+ at the cytosolic face, but was detected at Ca2+ concentrations as low as 10−7 m (open probability (P o ) = 0.11 ± 0.03, n= 8). Gadolinium decreased P o of the NSC channel from both the external and cytosolic side (IC50∼ 0.6 μm). NSC currents were decreased by amiloride (10 μm− 1 mm) and flufenamic acid (0.1 mm). The BK channel was also frequently (38%) observed in excised patches. In symmetrical 150 mm KCl conditions, the I-V relationship was linear with a conductance of 268 pS. The Goldman-Hodgkin-Katz equation for current carried solely by K+ could be fitted to the I-V relationship in asymmetrical K+ and Na+ solutions. The channel was impermeable to Cl− and N-methyl-d-glucamine. P o of the BK channel increased with depolarization of the membrane potential and with increasing cytosolic Ca2+. TEA (20 mm), charybdotoxin (100 nm) and Ba2+ (1 mm) but not amiloride (1 mm) reduced P o from the extracellular side. In contrast, external flufenamic acid (100 μm) increased P o and this effect was inhibited by charybdotoxin (100 nm). Flufenamic acid inhibited the inward short-circuit current measured by the vibrating probe and caused a transient outward current. We conclude that the NSC channel is Ca2+ activated, voltage-insensitive and involved in both constitutive K+ and Na+ reabsorption from endolymph while the BK channel might participate in the K+ pathway under stimulated conditions that produce an elevated intracellular Ca2+ or depolarized membrane potential.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Clinical & experimental allergy 31 (2001), S. 0 
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 2709-2717 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Alternating current losses in stacks of powder-in-tube-processed Bi2Sr2Ca2Cu3O10/Ag tapes were measured in perpendicular magnetic fields and compared with calculated hysteresis losses based on the critical-state model. Four main factors had to be taken into account for the calculations of the losses: (1) the inclusion of the area of the Ag sheath in determining the critical-current densities of the stacks, (2) the zero-applied-field critical currents Ic⊥(0) with truly perpendicular fields only, not the standard self-field critical current IcS(0), and (3) the field-dependent critical current Ic(H), e.g., the Kim's model, and (4) the subtraction of the frequency-dependent losses at very high fields. With these considerations, the agreement between the calculated and the measured values of the losses is excellent for fields beyond the full-penetration fields. However, these factors did not totally account for the low-field losses. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6229-6231 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The power loss (Pcv) was analyzed by combining two methods. The first, Pcv, is divided into hysteresis loss (Ph) and residual loss (Pr) from the frequency dependence of the power loss according to the method of Otsuki et al., and, second, the loss factors are attributed to domain wall motion (Pw) and the rotation magnetization (Prot) by adapting the method proposed by Visser et al. It was found that Pw coincides with Ph in the lower frequency range, but the difference between them becomes significant as frequency goes up. The higher value of Pw, in comparison with Ph in the higher frequency range, can be attributed to the enhancement of loss due to the dynamic motion of the domain wall (Pwd) by raising the frequency. The hysteresis loss dominates Pcv in the frequency range below 500 kHz, while Pwd becomes predominant factor in the higher frequency range more than 500 kHz. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford UK : Blackwell Science Ltd.
    Alimentary pharmacology & therapeutics 16 (2002), S. 0 
    ISSN: 1365-2036
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Gastrin is known to have stimulatory effects on gastric mucosa; however, long-term effect of gastrin stimulation is not well known.〈section xml:id="abs1-2"〉〈title type="main"〉Aim and methods:To investigate the long-term effect of hypergastrinaemia, we established hypergastrinaemic transgenic mice by introducing a mutated human gastrin gene. Homozygously transgene-expressing mice showed serum gastrin levels of more than 600 pg/mL.〈section xml:id="abs1-3"〉〈title type="main"〉Results:Neither progastrin nor glycine-extended gastrin titre elevation were observed in hypergastrinaemic transgenic mice. Stomachs from the 30–35-week-old transgenic mice were 30–50% heavier and their mucosa were markedly thicker than those of the controls. The hypertrophic gastric mucosa of hypergastrinaemic transgenic mice consisted of elongated pits with widespread proliferative zones, and comprised depleted glandular regions. In situ hybridization study indicated that expression of H, K-ATPase mRNA in parietal cells of hypergastrinaemic transgenic mice was markedly decreased. By gastrin binding assay in vivo, specific gastrin binding sites were observed in the mid-glandular region of hypergastrinaemic transgenic mice that consisted mainly of prepit cells.〈section xml:id="abs1-4"〉〈title type="main"〉Conclusions:These results suggest that long-term stimulation of gastrin increases the expression of CCK-B/gastrin receptors in the less-differentiated pit cells that are the main component of elongated gastric units, and lessens the well-differentiated characteristics of parietal cells.
    Type of Medium: Electronic Resource
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