Determination of selected quaternary ammonium compounds by liquid chromatography with mass spectrometry. Part I. Application to surface, waste and indirect discharge water samples in Austria

A method for simultaneous quantitative determination of alkyl benzyl, dialkyl and trialkyl quaternary ammonium compounds (QACs) has been developed, validated and subsequently applied to real water samples in Austria. The method employs liquid-liquid extraction (LLE) followed by liquid chromatography/tandem mass spectrometry (LC-MS/MS), using electrospray ionization (ESI) in positive mode. The overall method quantification limits range from 4 to 19ng/L for the enrichment of 500mL water samples and analyte recoveries are between 80 and 99%. The method was applied to 62 of the respective water samples without filtration to avoid the loss of the analytes due to the high adsorption capacity of these compounds. Maxima in the mg/L range, especially in the wastewater of hospitals and laundries, could be detected for the selected target compounds.     

The role of per-capita productivity in the evolution of small colony sizes in ants

The evolution of colony size in social insects is influenced by both extrinsic and colony-intrinsic factors. An important intrinsic trait, per-capita productivity, often declines in larger colonies. This pattern, known as Michener’s paradox, can limit the growth of insect societies. In this study, we first describe this problem, survey its occurrence across different ant species, and present a case study of eight cavity-dwelling ants with very small colony sizes. In these species, colonies might never reach sizes at which per-capita productivity decreases. However, in six out of the eight focal species, per-capita productivity did decline with increasing size, in accordance with other studies on per-capita productivity in ants. Several mechanisms, such as resource availability or nest-site limitation, may explain the decrease in per-capita productivity with increases in colony size in our focal species. In these central-place foragers, the individual foraging mode is expected to lead to an increase in travel time as colonies grow. We suggest that polydomy, the concomitant occupation of several nest sites, could serve as a potential strategy to overcome this limitation. Indeed, for one species, we show that polydomy can help to circumvent the reduction in productivity with increasing colony size, suggesting that limited resource availability causes the observed decrease in per-capita productivity. Finally, we discuss the influence of other factors, such as the nesting ecology and colony homeostasis, on the evolution of colony size in these cavity-dwelling ants.     

Atrazine induction of cytochrome P450 in Chironomus tentans larvae

Cytochrome P450-dependent aldrin epoxidation was characterized in third instar larvae of the aquatic midge, Chironomus tentans. Optimal in vitro assay conditions for the epoxidase were pH 7.6 and 31 degrees C. Activity was linear up to 40 min of incubation time and 0.5 mg microsomal protein per incubation. The activity was concentrated in the microsomal fraction of whole body homogenates and was NADPH-dependent. The effect of atrazine exposure on aldrin epoxidase was measured to determine if this herbicide induces cytochrome P450-dependent activity. Comparisons of control and atrazine-exposed midges indicated increased epoxidase activity as a result of atrazine exposure, and a 45 kDa protein of increased intensity was observed after SDS-PAGE of microsomal protein. The molecular weight of this protein was similar in size to cytochrome P450 enzymes reported for other insects. Heme staining of SDS-PAGE gels and immunochemical studies using a Drosophila melanogaster anti-P450 polyclonal antiserum, further support the cytochrome P450 nature of this inducible 45 kDa protein.     

Validation of a European standard for the determination of hexavalent chromium in solid material

A European standard for the determination of Cr(vi) in solid material has been elaborated in the framework of an international co-operation and finally validated in the course of an interlaboratory comparison. The procedure is based on the alkaline digestion prescribed by EPA method 3060A followed by ion chromatography and determines an operationally defined content of Cr(vi), including water-soluble and insoluble chromates. A preliminary robustness study was carried out in order to compare different extraction methodologies and to study the equivalency of different analytical methods for the determination of Cr(vi) in alkaline extracts of soil and waste materials. During an interlaboratory validation trial with 19 European laboratories a set of 4 samples (2 soil and 2 waste samples) was analysed to determine performance characteristics for different combinations of digestion and detection methods. With the procedures prescribed by the new European standard (EN 15192) acceptable results were obtained for both soil samples and one of the waste samples (sludge). However, for the second waste sample (fly ash) a large deviation in analytical results was observed. This indicates that particularly for waste materials a possible occurrence of strong matrix effects has to be considered and supplementary quality control data are needed in order to assess the validity of analytical results. The accuracy of the determination of Cr(vi) in solid matrices remains a challenging field in terms of maximum extraction efficiency and minimum species interconversion.     

Economically optimal nitrogen rate reduces soil residual nitrate

Post-harvest residual soil NO(3)-N (RSN) is susceptible to transfer to water resources. Practices that minimize RSN levels can reduce N loss to the environment. Our objectives were (i) to determine if the RSN after corn (Zea mays L.) harvest can be reduced if N fertilizer is applied at the economically optimal N rate (EONR) as compared to current producer practices in the midwestern USA and (ii) to compare RSN levels for N fertilizer rates below, at, and above the EONR. Six experiments were conducted in producer fields in three major soil areas (Mississippi Delta alluvial, deep loess, claypan) in Missouri over 2 yr. Predominant soil great groups were Albaqualfs, Argiudolls, Haplaquolls, and Fluvaquents. At four transects in each field, six treatment N rates from 0 to 280 kg N ha(-1) were applied, the EONR was determined, and the RSN was measured to a 0.9-m depth from five treatment plots. The EONR at sampling sites varied from 49 to 228 kg N ha(-1) depending on site and year. Estimated average RSN at the EONR was 33 kg N ha(-1) in the 0.9-m profile. This was at least 12 kg N ha(-1) lower than RSN at the producers' N rates. The RSN increased with increasing Delta EONR (total N applied - EONR). This relationship was best modeled by a plateau-linear function, with a low RSN plateau at N rates well below the EONR. A linear increase in RSN began anywhere from 65 kg N ha(-1) below the EONR to 20 kg N ha(-1) above the EONR at the three sites with good data resolution near the EONR. Applying N rates in excess of the EONR produced elevated RSN values in all six experiments. Our results suggest that applying the EONR will produce environmental benefits in an economically sound manner, and that continued attempts to develop methods for accurately predicting EONR are justified.     

Estimation of age at maturation and growth of Atlantic green turtles (Chelonia mydas) using skeletochronology

Despite the vast amount of research on threatened and endangered green turtle populations, some uncertainty regarding stage durations, growth rates, and age at maturation remains. We used skeletochronology to address this gap in knowledge for green turtle populations in the North Atlantic Ocean that use coastal waters along the southeastern U.S. as developmental habitat. Oceanic stage duration was estimated at 1–7 years ( [`(\textX)] \overline{\text{X}}  = 3 years). Several growth models, including von Bertalanffy, logistic, Gompertz, and power functions were evaluated for describing sex-specific length-at-age data. Ages at maturation estimated using mean size at nesting for females from each genetic sub-population contributing juveniles to this neritic foraging area were 44 years (Florida), 42.5 years (Costa Rica), and 42 years (Mexico), which were higher than previously reported ages. This implies that nesting populations comprising primarily individuals utilizing foraging grounds in the southeastern U.S. may take longer to recover than previously estimated.     

Turner syndrome-omphalocele association: Incidence,karyotype, phenotype and fetal outcome

Objective

Omphalocele is known to be associated with genetic anomalies like trisomy 13, 18 and Beckwith–Wiedemann syndrome, but not with Turner syndrome (TS). Our aim was to assess the incidence of omphalocele in fetuses with TS, the phenotype of this association with other anomalies, their karyotype, and the fetal outcomes.

Method

Retrospective multicenter study of fetuses with confirmed diagnosis of TS. Data were extracted from a detailed questionnaire sent to specialists in prenatal ultrasound.

Results

680 fetuses with TS were included in this analysis. Incidence of small omphalocele in fetuses diagnosed ≥12 weeks was 3.1%. Including fetuses diagnosed before 12 weeks, it was 5.1%. 97.1% (34/35) of the affected fetuses had one or more associated anomalies including increased nuchal translucency (≥3 mm) and/or cystic hygroma (94.3%), hydrops/skin edema (71.1%), and cardiac anomalies (40%). The karyotype was 45,X in all fetuses. Fetal outcomes were poor with only 1 fetus born alive.

Conclusion

TS with 45,X karyotype but not with X chromosome variants is associated with small omphalocele. Most of these fetuses have associated anomalies and a poor prognosis. Our data suggest an association of TS with omphalocele, which is evident from the first trimester.