Environmental Risk Assessment of Chemical Substances

According to the OECD, it is estimated that some 70000 synthetic chemicals are in daily use. This number is still growing. Some of these products (e.g. polychlorinated biphenyls or chlorofluorocarbons) have gained great public attention due to their unexpected undesirable long-term impact on the ecosystem. The industrialized nations have therefore implemented and enforced stringent laws, in order to control the use of potentially harmful substances.It is an almost impossible task to have the EU Base Set available for all existing substances. The EU and other organizations like OECD have therefore put together priority lists of potentially harmful high-volume chemicals which are assessed by experts. The last couple of years, a tremendous amount of work has been done to develop computer-based modeling systems to predict the environmental behavior and distribution of chemical substances.There are models around (e.g. Mackay, USES, TGD EU, and others) to describe environmental distribution (Predicted Environmental Concentration (PEC)) of nonionic and nonpolar substances. For a first assessment, only a few physical properties (MP, BP, SOL, and possibly pKa) are needed. For ionic and/or polar substances, expert know-how is required.For environmental toxicity (Predicted No Effect Concentration (PNEC)), however, the situation is far more complex. There are different modes of action for each trophic level (algae, crustacea, fish). Computer models with Quantitative Structure-Activity Relationship (QSAR) offer a scientifically attractive tool to predict aquatic toxicity and biodegradation. There are no models that are applicable to heterogeneous chemical classes without expert know-how. Further progress can therefore be expected.The result of an ERA for perchloroethylene with USES is presented, and the problems of the adequacy of the model parameters explained. Here too, a further improvement is addressed.QSARs are attractive tools to design products with improved environmental compatibility at the research stage even before the first synthesis. In order to achieve such an ambitious aim, QSAR models that also include expert rules and evaluated results and their dependence on molecular structures will have to be further developed

Root distribution and morphology of maize seedlings as affected by tillage and fertilizer placement

Suboptimal soil conditions are known to result in poor early growth of maize (Zea mays L.) in no-tillage (NT) systems in contrast with conventional tillage (CT) systems. However, most studies have generally focused on maize roots at later growth stages and/or do not give details on root morphology. In a 2-year field study at two locations (silt loam and loam soils) in the Swiss midlands, we investigated the impacts of tillage intensity, NT vs. CT, and NP-fertilizer sidebanding on the morphology, vertical and horizontal distribution, and nutrient uptake of maize roots at the V6 growth stage. The length density (RLD) and the length per diameter-class distribution (LDD) of the roots were determined from soil cores taken to a depth of 0.5 m and at distances of 0.05 and 0.15 m from both sides of the maize row. The temperature of the topsoil was lower, and the bulk density and penetration resistance were greater in the topsoil of NT compared with CT. The growth and the development of the shoot were slower in NT. RLD was greater and the mean root diameter smaller in CT than in NT, while the vertical and horizontal distribution of roots did not differ between CT and NT. RLD increased in the zone enriched by the sidebanded fertilizer, independent of the tillage system, but LDD did not change. The poorer growth of the roots and shoots of maize seedlings was presumably caused by the lower topsoil temperature in NT rather than by mechanical impedance. The placement of a starter fertilizer at planting under NT is emphasize

Irritierende Vielfalt in der instrumentellen Elementanalytik: Das Konzept ist immer dasselbe

Modern analytical chemistry relies on a multiplicity of different instrumental methods, their ranges of application being partially overlapping, partially supplementary. The universally utilizable dream method, which solves all possible problems does not exist. Nevertheless, every existing instrumental analytical method can be described as a modular composition including three steps: provocation, reaction, and detection. Based on this concept, the irritating multiplicity of existing analytical methods can be well surveyed

Assimilate transport in maize (Zea mays L.) seedlings at vertical low temperature gradients in the root zone

Even moderate chilling temperatures may cause important modifications in assimilate movement in maize seedlings from the shoot to the roots, but there is no information on long-distance transport of assimilates in plants subjected to vertical gradients of moderately low temperatures in the root zone. Seedlings of a chilling-tolerant (KW1074) and a chilling-sensitive inbred line (CM109) of maize were grown in a system that allowed the maintenance of temperature gradients between the topsoil (0-10 cm) and the subsoil (10-50 cm). After pregrowth at 24°C until the thirdleaf stage, plants were subjected to chilling-stress regimes for 6 d (17/17/17 °C, 17/17/12°C, 12/12/12°C, 12/12/17°C, air/topsoil/subsoil). The time taken for the assimilates to enter the phloem from the second leaf increased at low temperatures for both lines, but to a much greater extent in CM109. Although mainly influenced by air and topsoil temperature, low temperature in the subsoil also affected this trait in CM109. The speed of assimilate transport between the second leaf and the mesocotyl in KW1074 was strongly reduced by cool temperatures in the shoot and topsoil as well as by 12°C in the subsoil in CM109, because the latter line had a larger portion of its root system in the subsoil as compared to KW1074. The portion of assimilates allocated to the root decreased at low temperatures in both lines, but to a greater extent in CM 109, and was controlled mostly by the subsoil temperature. After rewarming, values of all measured parameters of assimilate transport returned to near pregrowth levels within a few day

The sensitivity of an interferon-γ release assay in microbiologically confirmed pediatric tuberculosis

This study aimed at determining the sensitivity of a whole blood interferon-γ release assay (IGRA) among children with microbiologically confirmed tuberculosis in a high-burden country. Children with a diagnosis of tuberculosis based on clinical and radiographic assessment were tested with an IGRA in addition to microbiologic examination of appropriate specimens for acid-fast bacilli, mycobacterial rRNA, and observation for growth of Mycobacterium tuberculosis on appropriate culture media. Of the 405 children with a clinical diagnosis of tuberculosis, 91 (22.5%) had microbiologically confirmed tuberculosis, of whom 81 were tested with an IGRA. A positive result was obtained in 43 (sensitivity 53.1%, 95% confidence interval 42.3 to 63.6%), uninfluenced by age, sex, or disease manifestation. Conclusions: The sensitivity of a whole blood interferon-γ release assay in microbiologically confirmed pediatric tuberculosis was low. An IGRA cannot, thus, be used as rule-in test, but it might be useful to rule in tuberculosis among children in whom tuberculosis is notoriously difficult to confirm microbiologically

Global analyses revealed age-related alterations in innate immune responses after stimulation of pathogen recognition receptors

Aging leads to dysregulation of multiple components of the immune system that results in increased susceptibility to infections and poor response to vaccines in the aging population. The dysfunctions of adaptive B and T cells are well documented, but the effect of aging on innate immunity remains incompletely understood. Using a heterogeneous population of peripheral blood mononuclear cells (PBMCs), we first undertook transcriptional profiling and found that PBMCs isolated from old individuals (≥ 65 years) exhibited a delayed and altered response to stimulation with TLR4, TLR7/8, and RIG-I agonists compared to cells obtained from adults (≤ 40 years). This delayed response to innate immune agonists resulted in the reduced production of pro-inflammatory and antiviral cytokines and chemokines including TNFα, IL-6, IL-1β, IFNα, IFNγ, CCL2, and CCL7. While the major monocyte and dendritic cell subsets did not change numerically with aging, activation of specific cell types was altered. PBMCs from old subjects also had a lower frequency of CD40+ monocytes, impaired up-regulation of PD-L1 on monocytes and T cells, and increased expression of PD-L2 and B7-H4 on B cells. The defective immune response to innate agonists adversely affected adaptive immunity as TLR-stimulated PBMCs (minus CD3 T cells) from old subjects elicited significantly lower levels of adult T-cell proliferation than those from adult subjects in an allogeneic mixed lymphocyte reaction (MLR). Collectively, these age-associated changes in cytokine, chemokine and interferon production, as well as co-stimulatory protein expression could contribute to the blunted memory B- and T-cell immune responses to vaccines and infections