Publications (46) View all
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Article: Tetrodotoxin blocks L-type Ca2+ channels in canine ventricular cardiomyocytes.
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ABSTRACT: Tetrodotoxin (TTX) is believed to be the most selective inhibitor of voltage-gated fast Na(+) channels in excitable tissues, including nerve, skeletal muscle, and heart, although TTX sensitivity of the latter is lower than the former by at least three orders of magnitude. In the present study, the TTX sensitivity of L-type Ca(2+) current (I (Ca)) was studied in isolated canine ventricular cells using conventional voltage clamp and action potential voltage clamp techniques. TTX was found to block I (Ca) in a reversible manner without altering inactivation kinetics of I (Ca). Fitting results to the Hill equation, an IC(50) value of 55 ± 2 μM was obtained with a Hill coefficient of unity (1.0 ± s0.04). The current was fully abolished by 1 μM nisoldipine, indicating that it was really I (Ca). Under action potential voltage clamp conditions, the TTX-sensitive current displayed the typical fingerprint of I (Ca), which was absent in the presence of nisoldipine. Stick-and-ball models for Cav1.2 and Nav1.5 channel proteins were constructed to explain the differences observed between action of TTX on cardiac I (Ca) and I (Na). This is the first report demonstrating TTX to interact with L-type calcium current in the heart.Pflügers Archiv - European Journal of Physiology 05/2012; 464(2):167-74. · 4.46 Impact Factor -
Article: Effects of the PKC inhibitors chelerythrine and bisindolylmaleimide I (GF 109203X) on delayed rectifier K+ currents.
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ABSTRACT: Protein kinase C (PKC) inhibitors are useful tools for studying PKC-dependent regulation of ion channels. For this purpose, high PKC specificity is a basic requirement excluding any direct interaction between the PKC inhibitor and the ion channel. In the present study, the effects of two frequently applied PKC inhibitors, chelerythine and bisindolylmaleimide I, were studied on the rapid and slow components of the delayed rectifier K(+) current (I(Kr) and I(Ks)) in canine ventricular cardiomyocytes and on the human ether-à-go-go-related gene (hERG) channels expressed in human embryonic kidney (HEK) cells. The whole cell version of the patch clamp technique was used in all experiments. Chelerythrine and bisindolylmaleimide I (both 1 μM) suppressed I(Kr) in canine ventricular cells. This inhibition developed rapidly, suggesting a direct drug-channel interaction. In HEK cells heterologously expressing hERG channels, chelerythrine and bisindolylmaleimide I blocked hERG current in a concentration-dependent manner, having EC(50) values of 0.11 ± 0.01 and 0.76 ± 0.04 μM, respectively. Both chelerythrine and bisindolylmaleimide I strongly modified gating kinetics of hERG--voltage dependence of activation was shifted towards more negative voltages and activation was accelerated. Deactivation was slowed by bisindolylmaleimide I but not by chelerythrine. I(Ks) was not significantly altered by bisindolylmaleimide I and chelerythrine. No significant effect of 0.1 μM bisindolylmaleimide I or 0.1 μM PMA (PKC activator) was observed on I(Kr) arguing against significant contribution of PKC to regulation of I(Kr). It is concluded that neither chelerythrine nor bisindolylmaleimide I is suitable for selective PKC blockade due to their direct blocking actions on the hERG channel.Archiv für Experimentelle Pathologie und Pharmakologie 02/2011; 383(2):141-8. · 2.65 Impact Factor -
Article: Answer to the "comment on functional consequences of Kv1.3 ion channel rearrangement into the immunological synapse" by Stefan Bittner et al. [Immunol. Lett. 125 (Aug 15 (2)) (2009) 156-157].
Immunology letters 03/2010; 129(1):47-9. · 2.91 Impact Factor -
Article: Quality of cryopreserved African catfish sperm following post-thaw storage
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ABSTRACT: Experiments were carried out to test the fertilizing capacity and viability of cryopreserved African catfish (Clarias gari- epinus) sperm following post-thaw storage at 4$,^circ$C and following activation with water. In the first experiment, cryopreserved sperm was thawed and stored in a refrigerator for time periods ranging from 0 to 96 h before being used for fertilization. In all cases sperm stored for 24 h resulted in the highest fertilization percentages (37 $pm$ 9%) which was sig- nificantly higher than that observed with sperm used for fertilization immediately after thawing (21 $pm$ 4%, P < 0.05). These observations were later confirmed by flow cytometric assessment of membrane integrity of spermatozoa which showed an increase of the percentage of membrane-intact cells from 2h post-thaw (66$pm$3%) to 26h (77$pm$3%). In the second experiment, thawed and fresh sperm of African catfish was activated with water and used for fertilization at different time periods post-activation ranging from 0 to 120 s. The highest fertilization rate with cryopreserved sperm (72 $pm$ 12%) was observed when eggs were fertilized with sperm activated for 20 s, however, sperm cells activated for 120 s were still able to fertilize eggs, albeit at a low rate (2 $pm$ 3%). It was also noted that in the second trial of experiment 2 cryopreserved sperm resulted in significantly higher fertilization percentages than freshly extracted semen (P < 0.05).Journal of Applied Icthyology. 01/2010; 26:737-741. -
Article: Shock‐induced triploidy and its effect on growth and gonad development of the European catfish, Silurus glanis L.
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ABSTRACT: Triloidy was induced in European catfish, Silurus glanis L., by cold-shocking eggs at 4°C for 30 and 40 min respectively, starting 5 min after fertilization. The hatching success of cold-shocked eggs was 25–30%. Cold shocks longer than 1 h caused total mortality. The triploid character of the cold-shocked European catfish was proved by karyological and red blood cell size analyses. The gonads of the triploid fish were significantly smaller than those of the diploids, while the growth rate values of the triploids were significantly higher than those of the diploids.Journal of Fish Biology 01/2006; 29(5):519 - 527. · 1.68 Impact Factor
