Ahmed Badr Osman

Lecturer - Lecturer of Animal Physiology

Faculty of science

Address: Sohag, Egypt


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Effects of seasonal acclimatization on thermal tolerance of inward currents in roach (Rutilus rutilus) cardiac myocytes
To test the hypothesis of temperature-dependent deterioration of electrical excitability (TDEE) (Vornanen, J Exp Biol 219:1941–1952, 2016), the role of sodium (_I_ Na) and calcium (_I_ Ca) currents in heat tolerance of cardiac excitability was examined in a eurythermic fish, the roach (_Rutilus rutilus_). Densities of cardiac _I_ Ca and _I_ Na and their acute heat tolerance were measured in ... Read more

Electrical excitability of roach (Rutilus rutilus) ventricular myocytes: effects of extracellular K+, temperature, and pacing frequency
Exercise, capture, and handling stress in fish can elevate extracellular K+ concentration ([K+]o) with potential impact on heart function in a temperature- and frequency-dependent manner. To this end, the effects of [K+]o on the excitability of ventricular myocytes of winter-acclimatized roach (_Rutilus rutilus_) (4 ± 0.5°C) were examined at different test temperatures and varying pacing rates. Frequencies corresponding to in ... Read more

Temperature, the abiotic master environmental factor, has a profound effect on the abundance and distribution of animals on the earth, in particular ecotherms. Ectothermic animals (fishes, frogs, reptiles, and invertebrate animals), cannot physiologically regulate their body temperature, and are therefore especially vulnerable to temperature changes to which they are not adapted but to which they might be exposed on the ... Read more

Effects of seasonal acclimatization on action potentials and sarcolemmal K+ currents in roach (Rutilus rutilus) cardiac myocytes
Temperature sensitivity of electrical excitability is a potential limiting factor for high temperature tolerance of ectotherms. The present study examines whether heat resistance of electrical excitability of cardiac myocytes is modified by seasonal thermal acclimatization in roach (_Rutilus rutilus_), a eurythermal teleost species. To this end, temperature dependencies of ventricular action potentials (APs), and atrial and ventricular K+ currents were ... Read more

Effects of seasonal acclimatization on temperature-dependence of cardiac excitability in the roach, Rutilus rutilus
Temperature-sensitivity of electrical excitability is a potential limiting factor for performance level and thermal tolerance of excitable tissues in ectothermic animals. In order to test whether rate and rhythm of the heart acclimatize to seasonal temperature changes, thermal sensitivity of cardiac excitation in a eurythermal teleost, the roach (_Rutilus rutilus_), was examined. Excitability of the heart was determined from _in ... Read more

Temperature dependence of cardiac sarcoplasmic reticulum and sarcolemma in the ventricle of catfish (Clarias gariepinus)
The present study was undertaken to examine the relative contribution of the SR-Ca2+release and sarcolemmal Ca2+ channels in developing the cardiac force at two different temperatures (20 and 30 °C) in the catfish (_Clarias gariepinus_). The sarcolemmal Ca2+ contribution of activator Ca2+ was greater at a test temperature of 30 °C as assessed by verapamil. Whereas the SR-Ca2+ contribution was ... Read more

Effect of changes in temperature on the force–frequency relationship in the heart of catfish (Clarias gariepinus)
An isometric ventricular preparation was used to investigate the effect of changes in temperature (10, 15, 20, 25 and 30 °C) on the cardiac contractility produced by increasing of frequency in the catfish heart. The ability of the ventricular preparation to develop the cardiac force at 10 °C continued regularly until a frequency of 1.0 Hz, whereas at 15, 20, ... Read more

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