Einzelreferate und Buchbesprechungen

Ohne Zusammenfassung     

Psychophysical assessment of sinusoidal whole-body vibration in z-axis between 0.6 and 5 Hz combined with different noise levels

Summary Nine healthy sitting males evaluated the intensity of vertical whole-body vibration (WBV) in z-axis at four frequencies (F1 = 0.63 Hz, F2 = 1.25 Hz, F3 = 2.5 Hz, F4 = 5 Hz) and two intensities (11 = 1 ms^–2 rms, 12 = 2 ms^–2 rms) by cross-modality matching (CMM). The subjects were simultaneously exposed to low-frequency noise at two levels (L1 = 65 dBA, L2 = 86 dBA). L1 and L2 were context conditions which did not have to be evaluated by CMM. The results indicate a flat response between F2 and F3; the sensitivity increases towards F1. Different exponents of Stevens' power law for the frequencies of WBV contradict the frequency range tested to be a sensory continuum. L2 caused practically significantly stronger sensations of the WBV-intensity from F1 to F3 (I1) and at F2 (I2). No synergistic effect of noise and WBV was shown at F3I2. Weighting factors were calculated for all exposure conditions using Stevens' power law. The weighting of F2 and F3 contradicts that of the International Standard ISO 2631-1985 (E). The results enable recommendations for the frequency weighting of WBV between 0.63 and 1 Hz, as well as for the equivalence of noise and WBV with combined exposure.This work was done in the Temporary International Research Team on combined Effects of Noise and Vibration of the Council of Mutual Economic Assistance of the Socialist Countries     

The positive inotropic response to milrinone in isolated human and guinea pig myocardium

Summary The bipyridine derivative, milrinone, produced positive inotropic effects in isolated, contracting right ventricular papillary muscles and left atria from guinea pigs as well as in human papillary muscle strips. The inotropic effect was biphasic in guinea pig papillary muscles (EC₅₀, high affinity, 1.5×10^–6 mol/l, about 35% of maximal effect; apparent EC₅₀, 3×10^–5 mol/l with a maximal effect at 2×10^–4 mol/l) but monophasic in guinea pig left atria (EC₅₀, 6×10^–5 mol/l) and in human papillary muscle strips (EC₅₀, 5.8×10^–5 mol/l). In guinea pig papillary muscles, reserpine pretreatment or l-practolol preincubation reduced the low concentration effect only. In the presence of l-practolol, carbachol reduced the low concentration effect only. In the presence of l-practolol, carbachol reduced but not abolished the inotropic effects of milrinone (3×10^–6 mol/l, 1×10^–4 mol/l) in both guinea pig and human myocardium. This antagonism was prevented by atropine preincubation. The maximum inotropic effect of milrinone was similar to that of ouabain and calcium in guinea pig myocardium but markedly less than either calcium or ouabain in human myocardium. Milrinone inhibited crude guinea pig and human cardiac phosphodiesterase activity in vitro but did not inhibit ³H-ouabain binding to partially purified human cardiac (Na⁺+K⁺)-ATPase-containing membranes.We conclude that the primary mode of action of milrinone in both guinea pig and human myocardium is through inhibition of phosphodiesterase. The reduced maximal inotropic effect of milrinone compared with calcium in human but not in guinea pig myocardium indicates basic differences between healthy animal and diseased human cardiac muscle.These studies were supported by the Deutsche Forschungsgemeinschaft (Er 65/4-4)The human heart papillary muscles were provided by: Prof. E. Kreuzer, Prof. B. Kemkes, Dr. C. Weinhold, Herzchirurgische Klinik der Universität, Klinikum Grosshadern, München, Federal Republic of GermanyParts of these studies have been presented at the Joint Meeting of the German, Dutch and Belgian Pharmacological Societies in Aachen, September 1985 (Brown et al. 1985) and at the Symposium on Cardiac Glycosides 1785–1985 in München, October 1985 (Brown et al. 1986a)