Physiologia Bohemoslovaca
-
Physiologia Bohemoslovaca · Jan 1985
Effects of hypoxia on respiratory defence reflexes. Effects of thirty hours' oxygen deficiency on cough, the expiration reflex and sneezing in awake cats.
The authors studied, in 11 awake adult cats, the parameters of the expiration reflex (ER), tracheobronchial (TB) and laryngopharyngeal (LPh) cough, the respiratory rate (f), tidal volume (VT), the end tidal fractional CO2 concentration (FETCO2), the pH, the blood gases and the heart rate during 30 hours' isobaric hypoxic hypoxia (FO2 = 0.11). During the whole 30 hours the cats developed hypocapnic hypoxemia, f remained unchanged and VT was markedly elevated. ⋯ The authors assume that some adaptation of the central mechanisms regulating the defence reflexes of the airways took place; this hypothesis is warranted, because an increase in the susceptibility of the cough centre during constant conditions of the stimulation of cough receptors would not be biologically expedient. The different changes in the intensity of respiratory defense reflexes in the acute and the prolonged phase of hypoxic hypoxia in the presence of identical changes in respiratory parameters are further indirect evidence pointing to the existence of functional differences between the respiratory centre and the cough centre.
-
Physiologia Bohemoslovaca · Jan 1983
Electromechanical relationships of rabbit papillary muscle under interpolated extrasystole conditions and after a pause.
The aim of the study was to describe and attempt to explain certain specific features of electromechanical coupling in the rabbit myocardium. Electromechanical correlations in the papillary muscles of the right ventricle of adult rabbit hearts were studied by a programmed stimulation technique. The duration of action potentials (AP) was measured in the plateau phase (Do, ms) and at -80 mV level (D80, ms), together with the intensity of the corresponding isometric contractions (MG, arbitrary units). ⋯ The MG value of the first contraction after the pause fell proportionally to log Tp. The AP recovered much more rapidly than contractility from the effect of the pause. In the discussion, an attempt is made to explain the found correlations on the basis of differences in the behaviour of the calcium current channel system in the rabbit myocardium and a commentary on electromechanical correlations is based on the hypothesis that the free sarcoplasmic calcium level determines both membrane electrogenesis and the inotropic state.
-
Physiologia Bohemoslovaca · Jan 1982
Modification of calcium fluxes by dimethyl sulfoxide and 2-butoxyethanol in sarcoplasmic reticulum vesicles: a possible mechanism for skeletal muscle relaxation induced by dimethyl sulfoxide.
In order to investigate the mechanism of skeletal muscle relaxation induced by dimethyl sulfoxide, 2-butoxyethanol and dimethyl sulfoxide were examined for their effects on 1) Ca2+ uptake into and efflux from sarcoplasmic reticulum vesicles prepared from rabbit fast skeletal muscle and crayfish tail muscle by the murexide method, 2) ATPase activities of rabbit reticulum vesicles, 3) the isolated phrenic nerve-diaphragm preparation of the rat and 4) crayfish opener muscle preparation. Ca2+ efflux rate from rabbit reticulum vesicles was markedly decreased with increasing concentrations (5-20% v/v) of dimethyl sulfoxide without affecting the maximum Ca2+ uptake by the reticulum. 2-Butoxyethanol showed quite contrary effects. ⋯ Antagonisms between dimethyl sulfoxide and caffeine were demonstrated either in contractions of crayfish opener muscles or in the Ca2+ release from crayfish sarcoplasmic reticulum vesicles. These results indicate a possibility that dimethyl sulfoxide reversibly induces skeletal muscle relaxation mainly in the sarcoplasmic reticulum by means of decreasing the rate and the amount of Ca2+ release from the reticulum.
-
Physiologia Bohemoslovaca · Jan 1978
Impedance of the arterial system in terms of Fourier harmonic analysis of the pulse wave.
The results obtained by analysis of pulse waves by means of Fourier harmonics in healthy subjects and patients with aortic insufficiency show good agreement between input impedance of the aorta and the initial segment of the femoral bed in both groups. This means that in this region there is no marked increase in impedance, which provides a favourable background for energy transfer (blood content) in the distal direction. ⋯ In patients with aortic insufficiency there is a marked decrease in amplitude of all higher harmonic frequencies. This practically means that the second harmonic is no longer the main accumulator of energy of the pulse wave as in healthy subjects, and the same is also true, to a proportionate degree, for the third, fourth and fifth harmonics.
-
Intrapleural pressure, the tracheal air flow and tidal volume were recorded simultaneously in pentobarbital-anaesthetized dogs and changes occurring in them during defensive reflexes elicited by mechanical stimulation of the mucosa of different parts of the respiratory tract were evaluated quantitatively. The results show that, in addition to coughing and sneezing provoked by inserting a nylon fibre into the tracheobronchial region, the larynx and the nose, further respiratory reflexes described in other mammals also appear in these animals. ⋯ The character of all these reflexes is typical and closely resembles their character in cats. Stimulation of the various parts of the respiratory tract sometimes evokes an apnoeic reaction instead of typical respiratory defensive reflexes.