Indicators for the exposure assessment of transformation products of organic micropollutants

Environmental transformation products of organic micropollutants have the potential to be similarly or even more mobile, persistent, ortoxic than their parent compounds. They should, therefore, be included in chemical hazard and risk assessment procedures as well as in the assessment of soil and water quality. To fulfill this requirement most efficiently, screening approaches that select relevant transformation products for detailed assessment are needed. This paper presents two process-based multimedia, multispecies models that allow us to quantitatively estimate the environmental fate of transformation products. The resulting exposure patterns are assessed with two indicators: joint persistence (JP), which describes the temporal extent of environmental exposure to a parent compound and its transformation products, and the predicted relative aquatic concentrations (RAC), which estimate the relative concentrations of parent compounds and their transformation products in surface water bodies. As a case study, JP and RAC are calculated for 16 pesticides and their relevant transformation products. The results for the JP indicator confirm the importance of considering transformation products in the assessment of overall persistence; for example, in the context of PBT assessments. Comparison of RAC results with monitoring data on herbicides and their transformation products shows the suitability of our approach for estimating relative concentrations in surface water, and as a consequence, its usefulness in identifying transformation products for future water quality monitoring programs. Transformation products of triketones and other highly used acidic herbicides are specifically identified as targets.     

Selecting scenarios to assess exposure of surface waters to veterinary medicines in Europe

Registering a veterinary medicinal product (VMP) in the European Union requires assessing its potential to contaminate surface waters (SW) on a European scale. VMP are spread to land in manure or excreted during grazing and may enter SW through runoff, erosion, or leaching. Since the factors driving these processes vary largely across Europe, it is necessary to identify characteristic conditions, so-called scenarios, under which VMP enter SW. These scenarios may guide the parameterization of mechanistic fate models to predict environmental concentrations for environmental risk assessment. A number of such scenarios for pesticides and VMP have been developed rather pragmatically. Here, we describe how a geo-referenced European database of driving factors was used to divide the European environment into groups with similar conditions for SW contamination by VMP. Out of these groups, relevant exposure scenarios in Europe were selected by a simple scoring system. Comparing these to the existing scenarios showed that a number of situations are not well covered. The newly identified scenarios are primarily located in hilly areas of Central Europe and the Mediterranean, and in Eastern European plains with a continental climate. We recommend that they are included in the technical guidelines for higher-tier assessment of VMP.     

Foodborne outbreak caused by Staphylococcus aureus: phenotypic and genotypic characterization of strains of food and human sources

An outbreak of staphylococcal food poisoning involving approximately 180 people occurred in Brodowski, S?o Paulo State, Brazil, in April 1998. Strains of Staphylococcus aureus isolated from foods and food handlers, implicated as the etiologic agent, were characterized with phenotypic (phage typing, antibiotic susceptibility test, and enterotoxin production), and genotypic (random amplified polymorphic DNA) characterization. Strains isolated from vegetable salad with mayonnaise sauce, broiled chicken, pasta in tomato sauce, and from the oropharyngeal secretions of five food handlers--A, B, C, H, and I--showed the same phage profile and antibiotic resistance. Random amplified polymorphic DNA generated 17 combined profiles with primers OPE-20 and OPA-7. The similarity of strains was analyzed by generating a dendrogram that classified the 59 strains of S. aureus into four major clusters (I, II, III, and IV). Strains from four food handlers (A, B, H, and I) and from vegetable salad with mayonnaise, broiled chicken, and pasta in tomato sauce showing the same phage type profile and resistance to antibiotics belonged to the same cluster and produced staphylococcal enterotoxin A. Therefore, these foods and food handlers were incriminated in the outbreak.     

Initiation of testicular tubulogenesis is controlled by neurotrophic tyrosine receptor kinases in a three-dimensional Sertoli cell aggregation assay

The first morphological sign of testicular differentiation is the formation of testis cords. Prior to cord formation, newly specified Sertoli cells establish adhesive junctions, and condensation of somatic cells along the surface epithelium of the genital ridge occurs. Here, we show that Sertoli cell aggregation is necessary for subsequent testis cord formation, and that neurotrophic tyrosine kinase receptors (NTRKs) regulate this process. In a three-dimensional cell culture assay, immature rat Sertoli cells aggregate to form large spherical aggregates (81.36+/-7.34 microm in diameter) in a highly organized, hexagonal arrangement (376.95+/-21.93 microm average distance between spherical aggregates). Exposure to NTRK inhibitors K252a and AG879 significantly disrupted Sertoli cell aggregation in a dose-dependent manner. Sertoli cells were prevented from establishing cell-cell contacts and from forming spherical aggregates. In vitro-derived spherical aggregates were xenografted into immunodeficient nude mice to investigate their developmental potential. In controls, seminiferous tubule-like structures showing polarized single-layered Sertoli cell epithelia, basement membranes, peritubular myoid cells surrounding the tubules, and lumen were observed in histological sections. By contrast, grafts from treatment groups were devoid of tubules and only few single Sertoli cells were present in xenografts after 4 weeks. Furthermore, the grafts were significantly smaller when Sertoli cell aggregation was disrupted by K252a in vitro (20.87 vs 6.63 mg; P<0.05). We conclude from these results that NTRK-regulated Sertoli-Sertoli cell contact is essential to the period of extensive growth and remodeling that occurs during testicular tubulogenesis, and our data indicate its potential function in fetal and prepubertal testis differentiation.     

Filler dispersion and electrical properties of polyamide 12/MWCNT-nanocomposites produced in reactive extrusion via anionic ring-opening polymerization

The reactive extrusion of lauryl lactam to polyamide 12 (PA12) of controlled molar mass was successfully performed in a microcompounder. The maximum residual monomer content was less than 1%. The in-situ polymerization in the presence of 1–5 wt.% multiwalled carbon nanotubes (MWCNTs) was studied and the processing conditions were optimized with respect to the electrical resistivity and MWCNT dispersion. Runs which yielded in higher molar mass PA12 resulted in better dispersion of MWCNTs, whereas nanocomposites with lower molar mass PA12 had lower electrical percolation thresholds (MWCNT concentration ∼1 wt.%). A high screw speed of 200 rpm was identified to cause best dispersion and the lowest percolation threshold.     

New Ruthenium Catalysts for Asymmetric Transfer Hydrogenation of Prochiral Ketones

Tridentate N,N,N‐pyridinebisimidazolines have been studied as new ligands for the enantioselective transfer hydrogenation of prochiral ketones. High yields and excellent enantioselectivity up to >99 % ee have been achieved with an in situ generated catalytic system containing dichlorotris(triphenylphosphine)ruthenium and 2,6‐bis‐([4R,5R]‐4,5‐diphenyl‐4,5‐dihydro‐1H‐imidazol‐2‐yl)‐pyridine ( 3a ) in the presence of sodium isopropoxide.     

Studies on apple and blueberry fruit constituents: do the polyphenols reach the colon after ingestion?

The aim of our studies was to determine the amount of polyphenols reaching the colon after oral intake of apple juice and blueberries. After a polyphenol-free diet healthy ileostomy volunteers consumed a polyphenol-rich cloudy apple juice while others consumed anthocyanin-rich blueberries. Ileostomy effluent was collected and polyphenols were identified using HPLC-DAD as well as HPLC-ESI-MS/MS; quantification was performed with HPLC-DAD. Most of the orally administered apple polyphenols were absorbed from or metabolized in the small intestine. Between 0 and 33% of the oral dose was recovered in the ileostomy bags with a maximum of excretion after 2 h. A higher amount of the blueberry anthocyanins under study (up to 85%, depending on the sugar moiety) were determined in the ileostomy bags and therefore would reach the colon under physiological circumstances. Such structure-related availability has to be considered when polyphenols are used in model systems to study potential preventive effects in colorectal diseases.