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2. Are there any differences in the excitation-contraction coupling of the working myocardium of adult and newborn Guinea-pigs?
- Creator:
- Fiala, P.
- Type:
- article, model:article, and TEXT
- Subject:
- Guinea-pig, ontogeny, action potential, contractility, and excitation-contraction coupling
- Language:
- English
- Description:
- Action potentials (APs) and the force of isometric contractions of the right ventricular papillary muscles were measured in adult and newborn guinea-pigs. The measurements were carried out in the steady state with the rate of stimulation of 0.1, 1, and 2 Hz, and further some measurements were done in which Sr2+ was substituted for Ca2- The duration of APs of the newborn animals without pharmacological treatment was significantly shorter in comparison with that of the adults at all the used stimulation frequencies. An analogous sensitivity was found in the contractile force to increased stimulation frequency and when the steady state stimulation was discontinued by the insertion of interpolated extrasystoles in papillary muscles of adult or newborn animals. The biphasic contractions of papillary muscles were evoked in both groups of animals by the incomplete substitution of Sr2+ by Ca2+ in the presence of isoprenaline. The early component of the biphasic contractions had a faster course as compared to the late component and disappeared in the presence of caffeine in both groups of animals. Our results suggest that the heart cells of newborn guinea-pigs probably possess the sarcoplasmic reticulum (SR), whose function does not differ in quality from that of the adult guinea-pigs. The postnatal prolongation of APs is therefore not probably the result of postnatal development changes of the functions of SR, but could be related to changes in the relations between the surface and volume of the heart cell during its growth.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3. Electrophysiological identification of tonic and phasic neurons in sensory dorsal root ganglion and their distinct implications inflammatory pain
- Creator:
- Yu, Y.-Q., Chen, X.-F., Yang, Y., Yang, F., and Chen, J.
- Format:
- print, bez média, and svazek
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, bolest, pain, action potential, dorsal root ganglion, tonic neuron, phasic neuron, 14, and 612
- Language:
- English
- Description:
- In the mammalian autonomic nervous system, tonic and phasic neurons can be differentiated on firing patterns in response to long depolarizing current pulse. However, the similar firing patterns in the somatic primary sensory neurons and their functional significance are not well investigated. Here, we identified two types of neurons innervating somatic sensory in rat dorsal root ganglia (DRG). Tonic neurons fire action potentials (APs) in an intensity-dependent manner, whereas phasic neurons typically generate only one AP firing at the onset of stimulation regardless of intensity. Combining retrograde labeling of somatic DRG neurons with fluorescent tracer DiI, we further find that these neurons demonstrate distinct changes under inflammatory pain states induced by complete Freund’s adjuvant (CFA) or bee venom toxin melittin. In tonic neurons, CFA and melittin treatments significantly decrease rheobase and AP durations (depolarization and repolarization), enhance amplitudes of overshoot and afterhyperpolarization (AHP), and increase the number of evoked action potentials. In phasic neurons, however, the same inflammation treatments cause fewer changes in these electrophysiological parameters except for the increased overshoot and decreased AP durations. In the present study, we find that tonic neurons are more hyperexcitable than phasic neurons after peripheral noxious inflammatory stimulation. The results indicate the distinct contributions of two types of DRG neurons in inflammatory pain., Y.-Q. Yu, X.-F. Chen, Y. Yang, F. Yang, J. Chen., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
4. Experimental methods for simultaneous measurement of action potentials and electrograms in isolated heart
- Creator:
- Jana Kolářová, Kateřina Fialová, Oto Janoušek, Marie Nováková, and Ivo Provazník
- Format:
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, fyziologie, physiology, isolated heart, action potential, electrogram, voltage sensitive dye, ratiometry, 14, and 612
- Language:
- English
- Description:
- Monophasic action potential (MAP) can be recorded from the heart surface by optical method based on fluorescence measurement. The motion of isolated heart during experiment caused additional noise in recorded signal. The motion artifact can be eliminated by ratiometric fluorescence emission measurements. This study is based on experiments in which optical MAP measurement is done by single-wavelength and dualwavelength measurement of fluorescence emission. Both recording setups are presented and their advantages and disadvantages are discussed. MAPs recorded by both methods from isolated rabbit hearts perfused according to Langendorff are presented. Simultaneous electrograms (EG) and MAPs recording are analyzed and measurement of velocity of impulse conduction through heart tissue is presented., J. Kolářová ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
5. Vegetable oils used as vitamin E vehicle affect the electrical activity of rat heart
- Creator:
- Ozdemir, S., Ayaz, M., Tuncer, T., Ugur, M., and Turan, B.
- Format:
- print, bez média, and svazek
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, vitamin E, fyziologie, physiology, action potential, corn oil, penaut oil, hazelnut oil, papillary muscle, atrial muscle, repolarization, 14, and 612
- Language:
- English
- Description:
- The aim of this study is to define the possible effects of vegetable oils used as vitamin E vehicle on the electrical activity of the rat heart. To test the possible effects of vitamin E vehicles we studied the effect of i.p. injected corn oil, hazelnut oil or peanut oil on the action potential parameters recorded in both papillary and left atrial muscle strips. Four experimental groups were used. The control group was injected (i.p.) with distilled water, while the three remaining groups received injections of corn oil, hazelnut oil, or peanut oil for five weeks (in a dose of 0.4 ml/kg/day - minimum amount of oil in which vitamin E could be dissolved). We used borosilicated (15-20 MΩ) capillary electrodes and intracellular action potentials (AP) were recorded in isolated papillary and left atrium muscle strips. While administration of three different types of vegetable oil had no significant effect on AP parameters of papillary muscle, they significantly prolonged the repolarization phase of AP in atrial strips. These results show that vegetable oils used as vitamin E vehicles may alter the electrical activity of the heart in a tissue-dependent manner. The present data indicate that the possible effect of vegetable oil vehicles should be kept in mind while evaluating the possible effects of in vivo vitamin E administration., S. Ozdemir, M. Ayaz, T. Tuncer, M. Ugur, B. Turan., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public