Reproduction disturbances of Brachionus calyciflorus (rotifer) for the screening of environmental endocrine disrupters

Rotifers and especially the Brachionus calyciflorus species have already shown advantages (e.g. good sensitivity, simplicity, ecological relevance, short generation time) for the chronic toxicity assessment of water pollutants. In this study, the B. calyciflorus three-day test was evaluated on ethinylestradiol, nonylphenol and testosterone for the determination of endocrine disrupting (reproductive) effects. Reproduction (intrinsic rate of population increase) and sex ratio (males/females and mictic females/amictic females) were explored and discussed as suitable endpoints. B. calyciflorus has shown a fair sensitivity to detect reproductive disrupting effects after exposure to ethinylestradiol, nonylphenol and testosterone. Population growth (intrinsic rate of population increase, r) and the ratio ovigerous females/non-ovigerous females are both suitable endpoints, whereas the occurrence of males was not frequent enough to be used as endpoint.     

The variation of risk estimates through pregnancy in second trimester maternal serum screening for Down syndrome

The variation of risk estimates in second trimester maternal serum screening for Down's syndrome has been shown to be considerable in quality control schemes, i.e. UKNEQAS. We studied the biological variation of risk estimates in 16 women through pregnancy. The maternal serum markers alpha-fetoprotein (AFP), human chorionic gonadotrophin (hCG), unconjugated estriol (uE3) and β-hCG were determined six times during late first to late second trimester, and the associated likelihood ratios for Down syndrome were calculated. The interpersonal variation of markers, as well as that of the likelihood ratio, was much greater than the intrapersonal variation. The average intrapersonal standard deviation (SD) of the triple test log likelihood ratio was 0.2291, corresponding to a central 95-percentile interval 0.36–2.81 of the likelihood ratio. The interpersonal SD of the log likelihood ratio was 0.5482, corresponding to a central 95-percentile interval 0.08–11.87 of the likelihood ratio. The large difference between the intra- and interpersonal variation makes it unlikely that biological variation through pregnancy is a major contributor to the variation of risk estimates obtained several times in the same pregnancy. Rather, improvements in analytical quality and laboratory management must be expected to result in reduced variation and, in consequence, better performance of screening. Copyright © 2002 John Wiley & Sons, Ltd.