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Autonomic dysfunction as a partial contributing factor to cardiovascular instability in jaundiced patients is often associated with increased serum bilirubin levels. Whether increased serum bilirubin levels could directly inhibit sympathetic ganglion transmission by blocking neuronal nicotinic acetylcholine receptors (nAChRs) remains to be elucidated. Conventional patch-clamp recordings were used to study the effect of bilirubin on nAChRs currents from enzymatically dissociated rat superior cervical ganglia (SCG) neurons. The results showed that low concnetrations (0.5 and 2 μM) of bilirubin enhanced the peak ACh-evoked currents, while high concentrations (3 to 5.5 μM) of bilirubin suppressed the currents with an IC50 of 4 ± 0.5 μM. In addition, bilirubin decreased the extent of desensitization of nAChRs in a concentration-dependent manner. This inhibitory effect of bilirubin on nAChRs channel currents was non-competitive and voltage independent. Bilirubin partly improved the inhibitory effect of forskolin on ACh-induced currents without affecting the action of H-89. These data suggest that the dual effects of enhancement and suppression of bilirubin on nAChR function may be ascribed to the action mechanism of positive allosteric modulation and direct blockade. Thus, suppression of sympathetic ganglionic transmission through postganglionic nAChRs inhibition may partially contribute to the adverse cardiovascular effects in jaundiced patients. [ABSTRACT FROM AUTHOR]

Haphazard packing of equal and unequal spheres can be performed for the spheres of molecular sieve material with a density of 1.80. The packing of such spheres in air is equivalent to that of natural grains in water. Packing concentrations of equal spheres have been obtained for different packing intensities. Unequal spheres can be regarded as equal ones in a wide range of diameter ratios, so far as the packing concentration is concerned. A threshold of diameter ratio exists at 0.70, below which the packing concentration is expected to increase. The variation curves of concentration vs. diameter ratio were established in the experiment. The result will help us to understand the process of sedimentation and the concentration of voids in sedimentary rocks. [ABSTRACT FROM AUTHOR]

The volumes per oxygen of some silicate melts have been calculated and then compared with those of silicate glasses. It is suggested that the volume of a silicate melt can be divided into two parts. One is contri buted by the silicon-oxygen network and the other by the 'oxides'. Variation patterns of VPOs suggest that the volume of the Si - O network generally remains unchanged and the expansion of the melt is caused mainly by the local expansion of the 'oxides'. It is further proposed that the radius of O shows little variation, in striking contrast to the radius of cations. The mechanism governing the expansion is discussed in detail. [ABSTRACT FROM AUTHOR]