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Summary:Taking the necessary precautions essential for accurate trace element analysis, the zinc concentrations of 227 samples of amniotic fluid taken at term were determined by means of neutron activation analysis. Half of the zinc was found to be bound to the particles present in amniotic fluid. In the control group (123 cases) the zinc concentrations ranged from 25-261 g/l for untreated samples and from 14-143 g/l when the samples were centrifuged for 10 min at 22000g prior to analysis. The values showed log-normal frequency distributions and were lower than any of the values published in the literature to date.No statistically significant differences could be found, when zinc concentrations of various risk groups (mothefs suffering from gestosis or diabetes mellitus, newborns hypo-or hypertrophic, twin births) were compared with the zinc concentration of the control group. The amniotic fluid zinc concentration is not, therefore, a suitable indicator for the diagnosis of distufbances of the embryonic development.

115m Cd 2+ -uptake and accumulation by the yeast Saccharomyces cerevisiae was rapid and largely dependent on the presence of glucose. From the time response after addition of glucose and from studies with energy poisons or with cycloheximide, it could be deduced that the observed effects were neither due to a cotransport system of glucose and Cd 2+ nor due to the biosynthesis of binding or transport proteins, but to an energy-dependent transport system (K m :0.3 mM, V max :5n mol/min x mg dry wt), being driven by the electrochemical potential across the plasma membrane.There was a good correlation between the influence of cadmium on the kinetics of cell growth and toxic effects of Cd 2+ on the plasma membrane H + -ATPase. This inhibition was strongly dependent on the experimental conditions. Cadmium ions were most effective at high pH and high magnesium concentrations. They enhanced K m , whereas V max was not affected significantly. Under favourable conditions we found a lowest effective concentration of Cd 2+ at <1μM and 50% inhibition at 3.5 ΜM. In contrast, CdCl 2 had no effect on glucose and purine transport systems.