Electrical pacemakerÏrhythmic activity has been observed and extensively studied in the brain and other body organs, yet with the exception of the heart, the underlying mechanisms responsible for this rhythmicity remain largely unresolved. Electrical pacemaking in smooth muscle syncytia has been interpreted by at least two different classes of models: one based on voltage-dependent mechanisms (see Tomita, 1981;Publicover & Sanders, 1989;Publicover, 1995) and the other on chemically based intracellular mechanisms (see Tomita, 1981; Daniel et al. 1994). More recent findings provide support for the latter type of mechanism, one which involves Ca¥ release from intracellular Ca¥ stores (Van Helden, 1993;Liu et al. 1995;Hashitani et al. 1996;Van Helden et al. 1996;Komori et al. 1993).Evidence for a Ca¥ store-based electrical pacemaker was first derived from studies of lymphatic smooth muscle (Van Helden, 1993), a tissue that exhibits strong vasomotion, and from rhythmically active single isolated smooth muscle cells (Komori et al. 1993). Studies on a syncytial smooth muscle (lymphatic vessels) provided evidence that the action potentials that led to the rhythmic constrictions were initiated by underlying pacemaker activity. This activity was found to arise through a summation of more elementary events referred to as spontaneous transient depolarizations (STDs). STDs also occurred in denervated tissues and had a pharmacology indicating that they arose through Ca¥ release from stores, which generated a transient inward current across the cell membrane. Consistent with this, Journal of Physiology (2000) 1. Intracellular recordings made in single bundle strips of a visceral smooth muscle revealed rhythmic spontaneous membrane depolarizations termed slow waves (SWs). These exhibited 'pacemaker' and 'regenerative' components composed of summations of more elementary events termed spontaneous transient depolarizations (STDs). 2. STDs and SWs persisted in the presence of tetrodotoxin, nifedipine and ryanodine, and upon brief exposure to Ca¥-free Cd¥-containing solutions; they were enhanced by ACh and blocked by BAPTA AM, cyclopiazonic acid and caffeine. SWs were also inhibited in heparinloaded strips. 3. SWs were observed over a wide range of membrane potentials (e.g. −80 to −45 mV) with increased frequencies at more depolarized potentials. 4. Regular spontaneous SW activity in this preparation began after 1-3 h superfusion of the tissue with physiological saline following the dissection procedure. Membrane depolarization applied before the onset of this activity induced bursts of STD-like events (termed the 'initial' response) which, when larger than threshold levels initiated regenerative responses. The combined initial-regenerative waveform was termed the SW-like action potential. 5. Voltage-induced responses exhibited large variable latencies (typical range 0·3-4 s), refractory periods of •11 s and a pharmacology that was indistinguishable from those of STDs and spontaneous SWs. 6. The data indicate that SWs arise through...

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Abstract. In this work the dependence of frequency of cardiac infarction, hypertensic crisis, psychological disturbance and behavioral disorders, bronchial asthma, cerebrovascular accident in Almaty on solar and magnetic activity at the period 2009-2013 was investigated. During this period there were 694336 cases of calls for emergency help. In order to appreciate the level of solar and geomagnetic activity Wolf number and k-index was used. Data was analysed by statistical method epochs superposition in order to find the correlations between geomagnetic activity and occurrence of listed above diseases. As the result it was established that in the day of magnetic storm and two days after number of patients directed to hospital with psychological disturbance and behavioral disorders increases. Number of patients directed to hospital with cardiac infarction increases the day before and remains some days after. Number of patients directed to hospital with hypertensic crisis increases in the day of magnetic storm. Number of patients directed to hospital with cerebrovascular accident increases a day after magnetic storm. What concerns of bronchial asthma the dependence is not so clear.