Estimating growth charts via nonparametric quantile regression: a practical framework with application in ecology

We discuss a practical and effective framework to estimate reference growth charts via regression quantiles. Inequality constraints are used to ensure both monotonicity and non-crossing of the estimated quantile curves and penalized splines are employed to model the nonlinear growth patterns with respect to age. A companion R package is presented and relevant code discussed to favour spreading and application of the proposed methods.     

Triadimefon Causes Branchial Arch Malformations in Xenopus laevis Embryos (5 pp)

- DOI: http://dx.doi.org/10.1065/espr2006.01.014 Background, Aims and Scope Triazole-derivatives are potent antifungal agents used as systemic agricultural fungicides and against fungal diseases in humans and domestic animals. They act by inhibiting the cytochrome P-450 conversion of lanosterol to ergosterol, thus resulting in faulty fungal cell wall synthesis. Some data have been published about the teratogenic activity of triazoles on rodent embryos: Hypoplasias, abnormal shape, agenesis of the branchial arches, for example, were reported as typical induced malformations. Unfortunately, no data are available on the embryotoxicity of these compounds in amphibians, despite the increasing concern among the scientific community about the phenomenon of global amphibian population declines. The aim of the present work is to evaluate the embryo-lethal and teratogenic potentials of Triadimefon (FON), a triazolederivative widely used as an antimycotic in agriculture, by the test FETAX (Frog Embryos Teratogenic Assay, Xenopus) with particular attention being paid to the analysis of branchial arch malformations. Methods Xenopus laevis embryos were exposed continuously from stage 9 to increasing concentrations of FON and analyzed at stage 47 for mortality and teratogenicity (group I) to determine the median lethal (LC50) and teratogenic (TC50) concentrations. Another two pools of larvae were exposed to FON for a 2 hour period at early gastrula (Group II) or neurula (Group III) stages to verify which period of development is the most sensitive to FON. The malformations observed were further investigated by histological section and cartilage staining with Alcian blue. Results and Discussion The assay has estimated LC50 and TC50 values of 63.8 μM and 2.73 μM, respectively; the resulting TI (Teratogenic Index = LC50/TC50) value of 23.4 has underlined the very high teratogenic risk associated with this compound. Neurulation was more sensitive to FON exposure than gastrulation, since the TC50 estimated values for group III (neurula exposed) specimens was 7.6 times lower than those of group II (gastrula exposed). Interestingly, for each group analyzed, 100% of malformed embryos showed alterations at branchial arch derived cartilages: Anterior cartilages were reduced, missing, fused or incorrectly positioned while gill cartilages were altered only in the most severely affected specimens. In some cases these malformations were associated with hyperpigmentation. Our results support the hypothesis that FON can interfere with Neural Crest Cell (NCC) migration, since craniofacial components and melanophores are derived from neural crest material. Conclusion In conclusion, our data show Triadimefon to be a potent teratogen able to induce specific craniofacial malformation in Xenopus laevis embryos, probably interfering with the NCC migration into the branchial mesenchyme. These results are also interesting for ecotoxicological reasons as FON, as well as other pesticides, are likely to be present in water systems near agricultural or urban areas which may serve as habitats for developing amphibians and fishes. Recommendation and Outlook Our results are in agreement with the data obtained on in vitro cultured rat embryos suggesting that the FON mechanism of action involves strongly conserved molecules. The choice of Xenopus laevis as the model organism allows us to extend the toxicological and teratological observations to a molecular level, in order to search for novel genes regulated by FON exposure.     

Pilot scale evaluation of the BABIU process – Upgrading of landfill gas or biogas with the use of MSWI bottom ash

Biogas or landfill gas can be converted to a high-grade gas rich in methane with the use of municipal solid waste incineration bottom ash as a reactant for fixation of CO₂ and H₂S. In order to verify results previously obtained at a laboratory scale with 65–90 kg of bottom ash (BA), several test runs were performed at a pilot scale, using 500–1000 kg of bottom ash and up to 9.2 N m³/h real landfill gas from a landfill in the Tuscany region (Italy). The input flow rate was altered. The best process performance was observed at a input flow rate of 3.7 N m³/(h t_BA). At this flow rate, the removal efficiencies for H₂S were approximately 99.5–99%.