Die Sorption von Phosphat an carbonatreichen Unterwasserböden

The sorption of phosphate by underwater soils rich in carbonate The phosphate sorption isotherms for carbonate rich under water soils (Unterwasserboden) can frequently be linearized by a modified Freundlich-isotherm when one assumes that, because of previously sorbed phosphate, the concentration of the equilibrium soil solution, P_1,0 is greater than 0. However, in many cases, the character of the phosphate sorption can be adequately determined with only one phosphate addition (P_s,500). Both methods show that for dried samples from under water soils, the samples from reduced horizons have a higher P sorption than for the associated oxidized horizons. This can be explained by the presence of very sorption active ferrihydrite which has precipitated from previously biologically reduced material.     

Quantitative Erfassung der reduzierten Substanzen in Unterwasserböden

Quantitative determination of reduced substances in subhydric soils The determination of reduced substances is possible by rapid oxidation with a diluted potassium dichromate/sulfuric acid solution at room temperature, and subsequent titration with FeSO₄ solution. These values (meq/100 ml of fresh sample) show a nonlinear, negative correlation with redox potential, and increase with increasing content of organic material. Sulfides, expressed as FeS, amount to appr. 50 % of the reduction equivalents. Subhydric soils rich in nutrients show an increasing amount of reduced substances with increasing depth, whereas oligotrophic and mesotrophic soils give no distinct depth function.     

Identification of Mycobacterium avium ssp. paratuberculosis infected dairy herds by environmental sampling

In herds with known prevalence (P) use of environmental sampling (ES) to detect Mycobacterium avium ssp. paratuberculosis (MAP) infected cattle herds was proofed in relation to P. In 31 MAP-infected free stall dairy herds and 15 non-infected herds P was defined by annually repeated whole herd testing by fecal culture (34 877 individual samples). Eight infected herds had a very low (> 0-2%), 14 a low (> 2-5%), four a medium (> 5-10%), and five a high P (> 10%). A mean number of nine environmental samples per herd were collected from the floor of lactating cows, milking, calving and sick cow areas and the crossover to the calf area. After twelve weeks cultivation on HEYM-medium with and without mycobactin positive samples were further characterized by PCR. All non-infected herds (100%) showed negative and 22 (71%) of the infected herds positive results in ES. Nine infected herds with negative ES results had a low P (0.04-4,04%). Proportion of positive ES depended on P and on sampling areas with 53.3% positive results in lactating cow areas and 45.2% in milking areas. For P > 5%, ES in these two areas caused a positive herd status; herds with P < 5% required sampling in the other areas too. The ES method has a herd sensitivity of 87% for dairy herds with P > 2% and provides an efficient tool to determine MAP infection status or herd prevalence.     

MRI studies of flow and dislocation of model NAPL in saturated and unsaturated sediments

In this article, we explore the possibilities of studying transport phenomena that involve non‐aqueous phase liquids (NAPL) by means of magnetic resonance imaging (MRI) with a paramagnetic contrast agent. We studied n‐octanol as a model NAPL, especially in alcohol flooding in a water‐saturated sediment, and flood‐drainage‐cycles in a temporally unsaturated sediment column. While the ‘natural’ relaxation time contrast between water and n‐octanol often allows a distinction of the two liquids in a quartz‐sand sediment, the use of Mn²⁺‐ions dissolved in the water phase as a ‘biphasic’ contrast agent allows much better discrimination between the different liquid phases and also considerably faster imaging. Using a 3D FLASH sequence, a NAPL‐saturated region can be visualized against a background of water‐saturated sediment in 11 s with a resolution of 1.9 × 1.9 × 3.2 mm³.     

Quality assurance of data collection and data processing in epidemiologic study data]

Quality assurance of the data generating processes in epidemiologic studies is a prerequisite for the internal validity of study results. This paper presents practical aspects of such a quality assurance system pertaining to the planning, data gathering, data entry and data processing phase of a study. It is concerned with data obtained in the framework of a project rather than with data accumulating continuously in private practices, research institutes or veterinary faculties. During the planning phase of a project, standard operating protocols should be developed that assure a reliable performance of observation, coding and data entry. The data base structure, consisting of tables, input validation rules and queries, should be predefined and well documented. A data safety concept will provide the necessary integrity, physical safety and availability of the data. The paper presents technical solutions to common data processing problems with emphasis on re-coding and relational data base facilities (Microsoft-ACCESS) using a hypothetical study on risk factors for mastitis.     

Identification of Plakortide E from the Caribbean Sponge Plakortis halichondroides as a Trypanocidal Protease Inhibitor using Bioactivity-Guided Fractionation

In this paper, we report new protease inhibitory activity of plakortide E towards cathepsins and cathepsin-like parasitic proteases. We further report on its anti-parasitic activity against Trypanosoma brucei with an IC₅₀ value of 5 μM and without cytotoxic effects against J774.1 macrophages at 100 μM concentration. Plakortide E was isolated from the sponge Plakortis halichondroides using enzyme assay-guided fractionation and identified by NMR spectroscopy and mass spectrometry. Furthermore, enzyme kinetic studies confirmed plakortide E as a non-competitive, slowly-binding, reversible inhibitor of rhodesain.     

Untersuchungen zum Nachweis latenter Kontaminationen vonErwinia carotovora var.atroseptica (van Hall) Dye an in vitro-Pflanzen von Kartoffeln

Zusammenfassung Es wurde geprüft, mit welcher Nachweissicherheit in vitro-Klone auf latenten Befall vonErwinia carotovora var.atroseptica (Eca) untersucht werden k?nnen. Als Testmethoden wurden ELISA-daten von in vitro-Pflanzen, Topfpflanzen und Knollen sowie der Bakteriennachweis an in vitro-Proben auf N?hrb?den verglichen. W?hrend die richtige Erfassung Eca-freier Klone mit allen Nachweismethoden fast fehlerfrei gelang, war die Ausgrenzung der positiven Proben mit ELISA teilweise nur mit unzureichender Testsicherheit m?glich. Die N?hrbodentests erwiesen sich als ungeeignet. Die besten Ergebnisse lieferte der ELISA-Knollentest, der aber wegen der Gefahr der Eca-Rekontamination ausscheidet. Aus Ermangelung rationeller Alternativen wird vorerst, trotz schwankender Nachweissicherheit, dem ELISA an in vitro-Pflanzen der Vorzug gegeben. Der Gefahr m?glicher Fehlaussagen wird durch eine mehrfach gestaffelte Kombination von Wiederholungen und Verwendung eines Auswertungsverfahrens mit rechnerischer Grenzwertermittlung entgegengewirkt.

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Summary Erwinia carotovora var.atroseptica (Eca) can survive for many years in tissue culture without signs of bacterial infection on the plants or of it being visible on the medium. Because the infection can be transmitted from one subcultivation to the next, there is a need for appropriate tests to detect latent contamination. Latent infection of in vitro plants, glasshouse plants and tubers by Eca was studied using ELISA and two nutrient media tests in trials to determine the levels of detection which could be achieved. Attempts were made to improve the interpretation of the ELISA results by comparing it with other methods of analysis. The plant material originated from in vitro material of known disease status. Sap samples for ELISA were pressed from whole in vitro plants, pieces from the stem bases of glasshouse plants and the heel-end of tubers. ELISA readings were taken at 405 nm using two photometers. The level used for discriminating between negative and positive results was based on calculating (mean and spread of values respectively). YEB-medium in liquid form and the Luria-Bertani Medium in liquid and solidified (agar) form were the test media (Table 1). Finely cut nodal segments of in vitro plants were placed in liquid media and incubated for five weeks. In vitro leaves which had been pierced were laid on the agar medium. ELISA proved to be inadequate when the results from repeated subcultures were compared (Table 2). The reproducibility of the results varied in sign and value. Readings obtained with negative samples were in better agreement with the disease status of the plants than those from positive ones. Using calculated separation levels gave sharper differentiation in the results than using fixed values. The ELISA results, interpreted on the basis of , varied considerably when applied to in vitro plants in the glasshouse (Fig. 1). Complete detection of the bacteria was only successful in the first test with in vitro plants and in tuber tests. Detection of latent Eca contamination was unsuccessful using the test nutrient media. Only 1 in 116 replicates gave the clouding expected with the nutrient media. There was strong growth of bacteria after two days in all tests with dilutions of pure cultures. False positives did not occur i.e. tests withErwinia-free clones remained clear. On the basis of these results a clear indication of latent Eca contamination on in vitro plants is not possible using ELISA, since the same clones gave positive or negative results depending on the time of testing. The poor reliability of the test must be due to the levels of the pathogen on in vitro plants (10²/g), lower than the detection level of ELISA (10³ cells ml⁻¹). The failure of latent bacteria to grow in the test nutrient media may be due to the attachment of the Eca pathogen to the cell wall structure of the in vitro plants. For reliable detection an enzymatic pre-treatment is presumably necessary, which would allow the pathogen to grow actively in the test media. No improvement of detection levels can be expected using ELISA. Glasshouse grown plants give inconsistent results similar to in vitro cultures. The degree of detection achievable with tuber tests renders it impractical, since the danger of recontamination by Eca during tuber multiplication in the glasshouse is too great. However other approaches to detection described in the literature are either uncertain or too expensive, and it appears that there is no alternative to ELISA for the detection of latent Eca contamination. The possible danger of false results can be counteracted to some extent by the combined use of replication and evaluations based on calculated separation values.

     

Barley roots are not constrained to large-sized biopores in the subsoil of a deep Haplic Luvisol

Using the profile wall method, we determined the root-length density (RLD) of barley roots growing in large-sized biopores (diameter >2 mm) and in the bulk soil of a Haplic Luvisol down to 200 cm of soil depth. The maximum bulk density in the soil profile (1.52 g?cm^?3) was recorded in the Bt horizon (41–115 cm of soil depth). The proportion of RLD in biopores over the total RLD increased with increasing soil depth down to the 45–75 or 75–105 cm of soil layer but then decreased again in deeper soil. In contrast to earlier investigations, the maximum percentage of RLD in biopores recorded in this study was only 25 %. Root sampling from individually dissected biopores confirmed that roots did not predominantly grow in biopores. Results suggest that roots can use biopores as preferred pathways for growth through rather compact soil layers, whereas they can possibly leave the biopore and re-enter the bulk soil in deeper, less compact layers.     

Bremia lactucae populations on cultivated lettuce originate from prickly lettuce and are interconnected with the wild pathosystem

European Journal of Plant Pathology - Maize rough dwarf disease (MRDD) is one of the most important viral diseases around the world. Rice black-streaked dwarf virus (RBSDV) and maize rough dwarf...     

Towards sustainable performance of urban horticulture: ten challenging fields of action for modern integrated pest management in cities

Journal of Plant Diseases and Protection - We identified ten current key challenges for plant protection in cities each of them belonging to a specific field of action of IPM in urban horticulture...