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  • 1
    Electronic Resource
    Electronic Resource
    Role of Calcium Loading in Early Afterdepolarizations Generated by Cs+ in Canine and Guinea Pig Purkinje Fibers (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 6 (1995), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Ca2+-Loading and EAD. introduction: Our previous observations indicate that the Na2+:Ca2+ exchange current (INa:Ca) plays an important role in early afterdepolarizations occurring at more negative Vm (L-EAD). The purpose of these studies was to examine the role of Ca2+-loading, which stimulates INa:Ca, in generation of L-EAD. Methods and Results: Purkinje strands and preparations of ventricular myocardium from dogs and guinea pigs were superfused with oxygenated physiologic buffer solutions at 37°C, To induce EADs, [K+]0 was reduced to 2.0 to 3.0 mM and [Cs+]0, (3.6 to 4.0 mM) was added at slow rates of ≤ 0.3 Hz. Isometric contraction in canine Purkinje strands and guinea pig papillary muscles doubled in 1-hour exposure to Cs+ and low [K+]0 at slow rates, and the uptake of 45Ca2+ was approximately doubled after 30 minutes. Forty-three percent of Purkinje fibers developed L-EAD after a latent period of 17 to 123 minutes of exposure. Ouabain (0.2 μM) suppressed LEAD within 10 minutes reversibly. Ca2+-loading (low [Na+]0 or high [Ca2+]0 for 5 to 10 minutes before exposure to Cs+, low [K+]0, and slow rates resulted in rapid development of L-EAD in all preparations during subsequent exposure. In Ca2+-loaded preparations, delayed afterdepolarizations (DADs) as well as L-EADs developed. Conclusion: Reduction of K+ currents with Cs+, low [K+]0, and slow rates induced L-EAD in a fraction of Purkinje fibers after a latent period during which Ca2+-loading of the sarcoplasmic reticulum occurred, while fibers preloaded with Ca2+ developed L-EAD rapidly and uniformly. These findings indicate that Ca2+-loading is a critical condition for the development of L-EAD. Early suppression of L-EAD by ouabain suggests a dependence of L-EAD on low [Na+]1. These findings implicate INa:Ca in the generation of L-EAD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1995.tb00356.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of isoproterenol on rubidium transport in slow- and fast-twitch muscles from euthyroid and hyperthyroid rats (1986)
    Springer
    Pflügers Archiv 407 (1986), S. 440-444 
    Details
    ISSN: 1432-2013
    Keywords: Skeletal muscle ; Hyperthyroidism ; Fibre types ; 86Rb influx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The influence of experimental hyperthyroidism on the catecholamine induced stimulation of rubidium ion transport in the soleus (SOL), a slow-twitch muscle and the extensor digitorum longus (EDL), a fast-twitch skeletal muscle of rats was studied. Thyroxine administration (800 μg/kg/day), for ten days induced a rise of ouabainsensitive86Rb uptake in SOL muscle, without affecting the ouabain-insensitive uptake, whereas both fractions of86Rb uptake were increased in EDL muscle from hyperthyroid rats. Isoproterenol (5 μmol/l) caused a two-fold rise in ouabain-sensitive Rb uptake of euthyroid SOL muscle, while in hyperthyroid SOL it could stimulate only the ouabain-insensitive fraction of86Rb influx. On the other hand, the stimulating action of isoproterenol on euthyroid EDL muscle was due to an enhancement of ouabain-insensitive Rb uptake, but in hyperthyroid EDL it failed to stimulate the ouabain-insensitive transport and caused a marked rise in ouabain-sensitive Rb uptake. The changes in catecholamine mediated transport properties in SOL muscle may be related to fibre type trans-formation induced by thyroid hormone, although in EDL the changes of catecholamine stimulation are unlikely due to fibre type conversion. Basal and isoproterenol stimulated cAMP levels were significantly reduced in both EDL and SOL muscles from hyperthyroid rats, in contrast with an insignificant decrease in net rubidium uptake caused by isoproterenol at the same concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652631
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  • 3
    Electronic Resource
    Electronic Resource
    The subcellular location of potassium flux pathways in frog skeletal muscle (1981)
    Springer
    Pflügers Archiv 390 (1981), S. 250-255 
    Details
    ISSN: 1432-2013
    Keywords: K-, Rb-uptake ; Ouabain ; Physostigmine ; Glycerol treatment ; Surface membrane ; Transverse tubules ; Frog muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The influence of ouabain and physostigmine on42K and86Rb uptake in isolated frog sartorii with normal [Na] i (12–14 mmol·kg−1 wet weight) and low [Na] i (6 mmol·kg−1 wet weight) was compared. Both in normal-sodium and in low-sodium muscles application of 10−3 M physostigmine reduces potassium influx by about 70%. About one fourth of potassium-uptake in normal-sodium muscles is inhibited by ouabain (10−4M) and only a very slight fraction of potassium uptake is ouabain-sensitive in low-sodium muscle. The effects of ouabain and physostigmine on42K influx are additive. The greater parts of the Rb-fluxes are through the ouabainsensitive pathway. Glycerol treatment has no effect on ouabain-sensitive channels although it inhibits markedly the K-flux through the physostigmine-sensitive pathway. The results suggest that the Na−K-ATPase is located in the surface membrane while most of the physostigmine-sensitive K-exchange is within the tubules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00658270
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  • 4
    Electronic Resource
    Electronic Resource
    The influence of catecholamines on Na, K transport in slow- and fast-twitch muscles of the rat (1983)
    Springer
    Pflügers Archiv 398 (1983), S. 236-240 
    Details
    ISSN: 1432-2013
    Keywords: Slow- and fast-twitch muscles ; Quabainsensitive and ouabain-insensitive86Rb influx ; 24Na and42K transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of catecholamines on active sodium and potassium transport was compared in slow- (SOL) and fasttwitch (EDL) skeletal muscles of the rat. Stimulation of active Na+-extrusion and K+-uptake induced by adrenaline (6–30 μmol · 1−1) and isoprenaline (1–40 μmol · l−1) was markedly greater in slow- than in fast-twitch muscle. In sodiumpreloaded muscles the maximal stimulation of24Na-efflux induced by adrenaline was about 2-fold higher in SOL than in EDL. Isoprenaline caused a 2.4-fold increase in ouabainsensitive86Rb influx in SOL muscle, but failed to alter the ouabain-sensitive influx in EDL. The stimulating action of isoprenaline on86Rb influx in EDL was due to an increase in the ouabain-insensitive fraction of Rb uptake. The effects of catecholamines of fast- and slow-twitch muscles were probably due to the accumulation of cyclic AMP, however the fact that there were no significant differences between the nucleotides levels in fast- and slow-twitch muscle suggests the participation of other mechanism as well. The results presented suggest that cyclic AMP-induced stimulation of ouabain-insensitive transport of cation in the isolated EDL muscle of the rat is similar to that of barnacle muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657158
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  • 5
    Electronic Resource
    Electronic Resource
    Total Synthesis of rac-Silandrin, an Antihepatotoxic Flavanolignan (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 105-109 
    Details
    ISSN: 0170-2041
    Keywords: Flavanolignan ; Silandrin ; Antihepatotoxic activity ; 1,4-Benzodioxane ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first synthesis of racemic silandrin (rac-1), which shows significant antihepatotoxic activity, has been accomplished via the key intermediate 9 prepared from the readily available starting materials caffeic acid ethyl ester (4) and coniferyl alcohol (5).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199319930119
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  • 6
    Electronic Resource
    Electronic Resource
    Secondary Fungal Metabolites and Their Biological Activity, VIIIPart VII: J. Sonnenbichler, I. Zetl, D. Schwarz, Phytochemistry 1996, in press.. - Partial Synthesis of Oosponol, an Antifungal Isocoumarin (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 211-212 
    Details
    ISSN: 0947-3440
    Keywords: Isocoumarin ; Oosponol ; Pseudomonas fluorescens ; Antibiotics ; Secondary fungal metabolite ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The partial synthesis of oosponol (4), which shows significant antibiotic activity, has been accomplished by enzyme catalyzed reactions including regioselective acetylation of (-)-oospoglycol (1) followed by an oxidation step and hydrolysis by a lipase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970130
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  • 7
    Electronic Resource
    Electronic Resource
    Total Synthesis of the Toxin Oosponol and of Structural Analogues and Investigation of Their Antibiotic Activities (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 773-777 
    Details
    ISSN: 0947-3440
    Keywords: Gloeophyllum abietinum ; Oosponol ; Isocoumarin ; Structure-activity relationships ; Antibiotics ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The toxic metabolite of the basidiomycete Gloeophyllum abietinum, oosponol (6b), and the structural analogues (Figure 1) were synthesised in order to investigate which partial structures of the molecules are responsible for their biological activities. Different organisms were employed to test the antibiotic activities of the analogues. From the results obtained with the synthetic analogues of oosponol (6b), it became evident that the toxicity of this fungal metabolite can be attributed to a vinylogous acid anhydride structure, which in nature is produced by dehydrogenation of the nontoxic precursor oospoglycol (7).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970422
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