Rapid testing leads to the underestimation of the scrapie prevalence in an affected sheep and goat flock

To obtain a more detailed understanding of the prevalence of classical scrapie infections in a heavily affected German sheep flock (composed of 603 sheep and 6 goats), we analysed 169 sheep and 6 goats that carried the genotypes susceptible to the disease and that were therefore culled following discovery of the index case. The initial tests were performed using the Biorad TeSeE ELISA and reactive results were verified by official confirmatory methods (OIE-immunoblot and/or immunohistochemistry (IHC)) to demonstrate the deposition of scrapie-associated PrP(Sc) in the brain stem (obex). This approach led to the discovery of 40 additional subclinically scrapie-infected sheep. Furthermore, peripheral lymphatic and nervous tissue samples of the 129 sheep and 6 goats with a negative CNS result were examined by IHC in order to identify any preclinical infections which had not already spread to the central nervous system (CNS). Using this approach we found 13 additional sheep with PrP(Sc) depositions in the gut-associated lymph nodes (GALT) as well as in the enteric nervous system. Moreover, in most of these cases PrP(Sc) was also deposited in the spleen and in the retropharyngeal and superficial cervical lymph nodes. Taken together, these results show a 30.3% infection prevalence in this scrapie-affected flock. Almost 7.4% of the infected animals harboured PrP(Sc) exclusively in the peripheral lymphatic and nervous tissue and were therefore missed by the currently used testing strategy.     

Structure of the ultrathin aluminum oxide film on NiAl(110)

The well-ordered aluminum oxide film formed by oxidation of the NiAl(110) surface is the most intensely studied metal surface oxide, but its structure was previously unknown. We determined the structure by extensive ab initio modeling and scanning tunneling microscopy experiments. Because the topmost aluminum atoms are pyramidally and tetrahedrally coordinated, the surface is different from all Al2O3 bulk phases. The film is a wide-gap insulator, although the overall stoichiometry of the film is not Al2O3 but Al10O13. We propose that the same building blocks can be found on the surfaces of bulk oxides, such as the reduced corundum (0001) surface.     

Effects of activated charcoal and tannin added to compost and to soil on carbon dioxide,nitrous oxide and ammonia volatilization

Given high mineralization rates of soil organic matter addition of organic fertilizers such as compost and manure is a particularly important component of soil fertility management under irrigated subtropical conditions as in Oman. However, such applications are often accompanied by high leaching and volatilization losses of N. Two experiments were therefore conducted to quantify the effects of additions of activated charcoal and tannin either to compost in the field or directly to the soil. In the compost experiment, activated charcoal and tannins were added to compost made from goat manure and plant material at a rate of either 0.5 t activated charcoal ha^?1, 0.8 t tannin extract ha^?1, or 0.6 t activated charcoal and tannin ha^?1 in a mixed application. Subsequently, emissions of CO₂, N₂O, and NH₃ volatilization were determined for 69 d of composting. The results were verified in a 20‐d soil incubation experiment in which C and N emissions from a soil amended with goat manure (equivalent to 135 kg N ha^?1) and additional amendments of either 3 t activated charcoal ha^?1, or 2 t tannin extract ha^?1, or the sum of both additives were determined. While activated charcoal failed to affect the measured parameters, both experiments showed that peaks of gaseous CO₂ and N emission were reduced and/or occurred at different times when tannin was applied to compost and soil. Application of tannins to compost reduced cumulative gaseous C emissions by 40% and of N by 36% compared with the non‐amended compost. Tannins applied directly to the soil reduced emission of N₂O by 17% and volatilization of NH₃ by 51% compared to the control. However, emissions of all gases increased in compost amended with activated charcoal, and the organic C concentration of the activated charcoal amended soil increased significantly compared to the control. Based on these results, tannins appear to be a promising amendment to reduce gaseous emissions from composts, particularly under subtropical conditions.     

Rapid degradation of gliadin peptides toxic for coeliac disease patients by proteases from germinating cereals

We report the isolation and characterisation of proteases from germinated wheat, rye and barley, and their ability to degrade gliadin peptides toxic for coeliac patients. It is shown for the first time that these proteases cleave these peptides rapidly into non-toxic fragments with less than nine amino acids. These proteases have distinct advantages when compared to bacterial or fungal proteases, and are promising candidates for the detoxification of gluten containing foods and for oral therapy for celiac patients.     

High-performance liquid chromatography-mass spectrometry profiling of phenolic compounds for evaluation of olive oil bitterness and pungency

Bitterness and pungency are important parameters for olive oil quality. Therefore, two instrumental methods for evaluation of these taste attributes were developed. The first one is based on the photometric measurement of total phenolic compounds content, whereas the second one is based on the semiquantitative evaluation of hydrophilic compounds by high-performance liquid chromatography-mass spectrometry (HPLC-MS). Evaluation of total phenolic compounds content was performed by a modified method for the determination of the K(225) value using a more specific detection based on the pH value dependency of absorbance coefficients of phenols at λ = 274 nm. The latter method was not suitable for correct prediction, because no significant correlation between bitterness/pungency and total phenolic compounds content could be found. For the second method, areas of 25 peaks detected in 54 olive oil samples by a HPLC-MS profiling method were correlated with the bitterness and pungency by partial least-squares regression. Six compounds (oleuropein aglycon, ligstroside aglycon, decarboxymethyl oleuropein aglycon, decarboxymethyl ligstroside aglycon, elenolic acid, and elenolic acid methyl ester) show high correlations to bitterness and pungency. The computed model using these six compounds was able to predict bitterness and pungency of olive oil in the error margin of the sensory evaluation (±0.5) for most of the samples.     

Quality evaluation of olive oil by statistical analysis of multicomponent stable isotope dilution assay data of aroma active compounds

An instrumental method for the evaluation of olive oil quality was developed. Twenty-one relevant aroma active compounds were quantified in 95 olive oil samples of different quality by headspace solid phase microextraction (HS-SPME) and dynamic headspace coupled to GC-MS. On the basis of these stable isotope dilution assay results, statistical evaluation by partial least-squares discriminant analysis (PLS-DA) was performed. Important variables were the odor activity values of ethyl isobutanoate, ethyl 2-methylbutanoate, 3-methylbutanol, butyric acid, E,E-2,4-decadienal, hexanoic acid, guaiacol, 2-phenylethanol, and the sum of the odor activity values of Z-3-hexenal, E-2-hexenal, Z-3-hexenyl acetate, and Z-3-hexenol. Classification performed with these variables predicted 88% of the olive oils' quality correctly. Additionally, the aroma compounds, which are characteristic for some off-flavors, were dissolved in refined plant oil. Sensory evaluation of these models demonstrated that the off-flavors rancid, fusty, and vinegary could be successfully simulated by a limited number of odorants.     

Rhizodeposition: Its contribution to microbial growth and carbon and nitrogen turnover within the rhizosphere

A greenhouse rhizobox experiment was carried out to investigate the fate and turnover of ¹³C‐ and ¹⁵N‐labeled rhizodeposits within a rhizosphere gradient from 0–8 mm distance to the roots of wheat. Rhizosphere soil layers from 0–1, 1–2, 2–3, 3–4, 4–6, and 6–8 mm distance to separated roots were investigated in an incubation experiment (42 d, 15°C) for changes in total C and N and that derived from rhizodeposition in total soil, in soil microbial biomass, and in the 0.05 M K₂SO₄–extractable soil fraction. CO₂‐C respiration in total and that derived from rhizodeposition were measured from the incubated rhizosphere soil samples. Rhizodeposition C was detected in rhizosphere soil up to 4–6 mm distance from the separated roots. Rhizodeposition N was only detected in the rhizosphere soils up to 3–4 mm distance from the roots. Microbial biomass C and N was increased with increasing proximity to the separated roots. Beside ¹³C and ¹⁵N derived from rhizodeposits, unlabeled soil C and N (native SOM) were incorporated into the growing microbial biomass towards the roots, indicating a distinct acceleration of soil organic matter (SOM) decomposition and N immobilization into the growing microbial biomass, even under the competition of plant growth. During the soil incubation, microbial biomass C and N decreased in all samples. Any decrease in microbial biomass C and N in the incubated rhizosphere soil layers is attributed mainly to a decrease of unlabeled (native) C and N, whereas the main portion of previously incorporated rhizodeposition C and N during the plant growth period remained immobilized in the microbial biomass during the incubation. Mineralization of native SOM C and N was enhanced within the entire investigated rhizosphere gradient. The results indicate complex interactions between substrate input derived from rhizodeposition, microbial growth, and accelerated C and N turnover, including the decomposition of native SOM (i.e., rhizosphere priming effects) at a high spatial resolution from the roots.     

Compost and phosphorus amendments for stimulating microorganisms and growth of ryegrass in a Ferralsol and a Luvisol

A greenhouse pot experiment was carried out to investigate the effects of different P‐fertilizer application forms (triple superphosphate [TSP], compost + TSP, TSP‐enriched compost) on the growth of ryegrass and the soil microbial biomass. The fertilizers were applied at equivalent doses for all nutrients to a neutral Luvisol in comparison with an acidic Ferralsol. Fertilizer application led to significantly increased contents of microbial biomass C, N, and P. Furthermore, yields of shoot C and root C, and concentrations of P, Ca, Mg, K, Fe, and Mn in shoots and roots were significantly increased. These increases always followed the order TSP < compost + TSP < TSP‐enriched compost. Sole TSP application led only to maximum concentrations of N and S. In the Ferralsol, TSP had only minimal positive effect on the P concentration of the grass shoots. The positive effect of TSP‐enriched compost, i.e., incubating TSP together with compost for 24 h, did not differ between the neutral Luvisol and the acidic Ferralsol, i.e., the effect is independent of the soil type. Consequently, soluble inorganic P fertilizer should generally be mixed into an organic fertilizer before application to soil.     

Initial decomposition of post-harvest crown and root residues of poplars as affected by N availability and particle size

An incubation experiment was carried out to investigate the impacts of residue particle size and N application on the decomposition of post-harvest residues of fast-growing poplar tree plantations as well as on the microbial biomass. Crown and root residues, differing in their C/N ratios (crown 285, root 94), were ground to two particle sizes and incubated with and without application of inorganic nitrogen (N) for 42 days in a tilled soil layer from a poplar plantation after 1 year of re-conversion to arable land. Carbon and N mineralization of the residues, microbial biomass C and N, ergosterol contents, and recovery of unused substrate as particulate organic matter (POM) were determined. Carbon mineralization of the residues accounted for 26 to 29 % of added C and caused a strong N immobilization, which further increased after N addition. N immobilization in the control soil showed that even 1 year after re-conversion, fine harvest residues still remaining in the soil were a sink for mineral N. Irrespective of the particle size, C mineralization increased only for crown residues after application of N. Nevertheless, the overall decrease in amounts of POM-C and a concurrent decrease of the C/N ratio in the POM demonstrate the mineralization of easily available components of woody residues. Microbial biomass significantly decreased during incubation, but higher cumulative CO₂ respiration after N application suggests an increased microbial turnover. Higher ergosterol to microbial biomass C ratios after residue incorporation points to a higher contribution of saprotrophic fungi in the microbial community, but fungal biomass was lower after N addition.