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  • 1
    Electronic Resource
    Electronic Resource
    Sarcoplasmic Reticulum Ca2+ Release in Rat Slow- and Fast-Twitch Muscles (1996)
    Springer
    The journal of membrane biology 151 (1996), S. 123-130 
    Details
    ISSN: 1432-1424
    Keywords: Key words: Skeletal muscle — Sarcoplasmic reticulum — Calcium release — Soleus — Slow-twitch muscle — Dihydropyridine receptor — Ryanodine receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. The same isoform of ryanodine receptor (RYR1) is expressed in both fast and slow mammalian skeletal muscles. However, differences in contractile activation and calcium release kinetics in intact and skinned fibers have been reported. In this work, intracellular Ca2+ transients were measured in soleus and extensor digitorum longus (EDL) single muscle fibers using mag-fura-2 (K D for Ca2+= 49 μm) as Ca2+ fluorescent indicator. Fibers were voltage-clamped at V h =−90 mV and sarcoplasmic reticulum calcium release was measured at the peak (a) and at the end (b) of 200 msec pulses at +10 mV. Values of a-b and b were assumed to correspond to Ca2+-gated and voltage-gated Ca2+ release, respectively. Ratios (b/a-b) in soleus and EDL fibers were 0.41 ± 0.05 and 1.01 ± 0.13 (n= 12), respectively. This result suggested that the proportion of dihydropyridine receptor (DHPR)-linked and unlinked RYRs is different in soleus and EDL muscle. The number of DHPR and RYR were determined by measuring high-affinity [3H]PN200-110 and [3H]ryanodine binding in soleus and EDL rat muscle homogenates. The B max values corresponded to a PN200-110/ryanodine binding ratio of 0.34 ± 0.05 and 0.92 ± 0.11 for soleus and EDL muscles (n= 4–8), respectively. These data suggest that soleus muscle has a larger calcium-gated calcium release component and a larger proportion of DHPR-unlinked RYRs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002329900063
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of 2,3-Butanedione 2-Monoxime on Ca2+ Release Channels (Ryanodine Receptors) of Cardiac and Skeletal Muscle (1999)
    Springer
    The journal of membrane biology 169 (1999), S. 189-198 
    Details
    ISSN: 1432-1424
    Keywords: Key words: Ca2+ release channel — Ryanodine receptor — Sarcoplasmic reticulum — 2,3-butanedione 2-monoxime — Skeletal muscle — Cardiac muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Single channel and [3H]ryanodine binding measurements were performed to test for a direct functional interaction between 2,3-butanedione 2-monoxime (BDM) and the skeletal and cardiac muscle sarcoplasmic reticulum Ca2+ release channels (ryanodine receptors). Single channel measurements were carried out in symmetric 0.25 m KCl media using the planar lipid bilayer method. BDM (1–10 mm) activated suboptimally Ca2+-activated (0.5–1 μm free Ca2+) single, purified and native cardiac and skeletal release channels in a concentration-dependent manner by increasing the number of channel events without a change of single channel conductances. BDM activated the two channel isoforms when added to either side of the bilayer. At a maximally activating cytosolic Ca2+ concentration of 20 μm, BDM was without effect on the cardiac channel, whereas it inhibited skeletal channel activities with IC50≈ 2.5 mm. In agreement with single channel measurements, high-affinity [3H]ryanodine binding to the two channel isoforms was increased in a concentration-dependent manner at ≤1 μm Ca2+. BDM was without a noticeable effect at low (≤0.01 μm) Ca2+ concentrations. At 20 μm Ca2+, BDM inhibited the skeletal but not cardiac channel. These results suggest that BDM regulates the Ca2+ release channels from the sarcoplasmic reticulum of skeletal and cardiac muscle in a concentration, Ca2+ and tissue-dependent manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002329900530
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Supercritical fluid extraction combined with solid phase extraction as sample preparation technique for the analysis of β-blockers in serum and urine (1998)
    Springer
    Fresenius' journal of analytical chemistry 360 (1998), S. 618-621 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A method is developed for the determination of β-blockers in serum and urine at levels of 0.5 μg/mL. The technique uses a combination of solid phase extraction (SPE) with in situ derivatization and supercritical fluid extraction (SFE) with subsequent gas chromatography mass spectrometry. The optimization of the SFE step shows that a static extraction period can be eliminated. The method gives good linearity (r = 0.991–0.999) and repeatability in the concentration range of 0.5 to 5 μg/mL. Relative standard deviations for oxprenolol, propanolol and metoprolol were less than 5% in serum and 5–11% in urine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050769
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    Paper (German National Licenses)
    Fulltext
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