Chiral perturbation theory and the 1/N_c-expansion

We briefly review the effective theory that describes the low energy properties of QCD with three light quarks and a large number of colours, N_c, and then discuss the mechanisms that forbid the Kaplan-Manohar transformation in this framework.Comment: 2 pages. Talk given at the Workshop "Chiral Dynamics 2000: Theory and Experiment", Newport News, VA, USA, July 17-22, 200

Degradation and metabolism of fenoxaprop-P-ethyl in sensitive and resistant populations of Alopecurus myosuroides

Blackgrass (Alopecurus myosuroides) is one of the most economically important weeds in Europe. Because of the development and distribution of herbicide resistant populations the control of this weed has become a serious challenge in agriculture. In recent years a reduced efficacy of fenoxaprop-P-ethyl towards A. myosuroides has been observed. To investigate the degradation of the active substance fenoxaprop-P-ethyl in A. myosuroides, four populations were grown in the greenhouse: One herbicide sensitive population, two populations with a non-target-site resistance (NTSR) and one population with a target-site resistance (TSR). For dose response studies the plants were treated with different dosages of fenoxaprop-P-ethyl and dry weight was determined after three weeks. For the NTSR populations resistance factors of 76 and 2 could be calculated based on ED50 values. The development of the TSR plants was not restricted by the herbicide treatment, not even with the highest dosage. For the degradation and metabolism studies plants were treated with fenoxaprop-P-ethyl and harvested for laboratory analysis 2, 8, 24, 48 and 96 hours after treatment. The active substance degraded within 96 hours without any significant differences between the populations. Two hours after herbicide treatment a metabolite could be identified and quantified in all populations. The mean contents at eight and 24 hours after treatment differed significantly between the populations. Results have shown that the metabolism of fenoxaprop-P-ethyl to fenoxaprop-P is very similar in the tested populations although they have different resistance mechanisms.  Further studies are intended to show if the populations differ in the formation of other unknown metabolites.  Keywords: ACCase resistance, aryloxyphenoxypropionates (AOPPs), herbicide metabolism, non-target-site resistance (NTSR) Abbau und Metabolismus von Fenoxaprop-P-ethyl in sensitiven und resistenten Populationen von Alopecurus myosuroides Zusammenfassung  Ackerfuchsschwanz (Alopecurus myosuroides) ist in Europa eines der Ungräser mit der größten wirtschaftlichen Bedeutung. Durch die Entwicklung und Ausbreitung resistenter Populationen wurde die Bekämpfung zu einer ernstzunehmenden Herausforderung in der Landwirtschaft. Seit einigen Jahren wird eine zunehmende Wirkungsschwäche von Fenoxaprop-P-ethyl gegenüber A. myosuroides beobachtet. Um das Abbauverhalten des Wirkstoffes in A. myosuroides zu untersuchen, wurden vier Populationen im Gewächshaus angezogen. Neben einem sensitiven Standard wurden für diese Untersuchung zwei Populationen mit einer nicht-wirkortspezifischen Resistenz (NTSR), sowie eine Population mit einer wirkortspezifischen Resistenz (TSR) verwendet. Für Dosis-Wirkungsversuche wurden die Pflanzen mit unterschiedlichen Konzentrationen des Wirkstoffs Fenoxaprop-P-ethyl behandelt und das Trockengewicht nach drei Wochen ermittelt. Basierend auf ED50-Werten konnten Resistenzfaktoren von 76 und 2 für die NTSR Populationen berechnet werden. Die Entwicklung der TSR Pflanzen wurde durch die Herbizid Behandlung nicht nachweisbar beeinflusst. Für die Abbau- und Metabolismusstudien wurden die Pflanzen mit Fenoxaprop-P-ethyl behandelt und anschließend nach 2, 8, 24, 48 und 96 Stunden geerntet und im Labor aufgearbeitet. Der Wirkstoff wurde nach 96 Stunden fast vollständig abgebaut ohne signifikante Unterschiede zwischen den Populationen. Zwei Stunden nach Herbizid Applikation konnte ein Metabolit des Wirkstoffes in allen Populationen identifiziert und quantifiziert werden. Die Gehalte des Metaboliten in den Populationen unterscheiden sich nach 8 und nach 24 Stunden signifikant voneinander. Die Ergebnisse zeigen, dass der Metabolismus von Fenoxaprop-P-ethyl zu Fenoxaprop-P, unabhängig vom Resistenzmechanismus sehr ähnlich ist. Weitere Studien sollen zeigen, ob sich die Populationen durch die Bildung von anderen, unbekannten Metaboliten unterscheiden. Stichwörter: ACCase-Resistenz, Aryloxyphenoxypropionate (AOPPs), Metabolismus, nicht-wirkortspezifischen Resistenz (NTSR

Cytokeratin 18 expression in immature Sertoli cells: co-localization with interstitial lymphocytic infiltrates.

Although multiple interactions of seminiferous tubules and the interstitial testicular tissue are known, correlation of cytokeratin 18 expressing Sertoli cells with interstitial changes has still not yet been reported. Considering this fact, we focused our investigation on changes of the adjacent interstitial tissue. A total sample of 51 testicular biopsies (from infertile patients) showing mixed atrophy was examined immunohistochemically with antibodies against cytokeratin 18, vimentin, L26/CD20, CD4 and CD8. Twenty-one of the 51 cases showed single seminiferous tubules with Sertoli cells expressing cytokeratin 18. These 21 tubules consistently exhibit either spermatogenic arrest at the level of spermatogonia or only immature Sertoli cells. In the adjacent interstitial tissue of 8 of the 21 cytokeratin 18 positive tubules (39%) striking inflammatory infiltrates--predominantly expressing L26/CD20 typical for B lymphocytes and CD8 typical for T suppressor lymphocytes--were detected. These findings underline that tubules with cytokeratin 18 expressing Sertoli cells exhibit early spermatogenic arrest or only few remaining Sertoli cells. Additionally, we observed a remarkable co-localization of these tubules with lymphocytic infiltrates of the adjacent interstitial tissue

Status and development of ACCase and ALS inhibitor resistant black-grass (Alopecurus myosuroides Huds.) in neighboring fields in Germany

Neighboring fields in three local areas of southern Germany have been investigated for the infestation level and herbicide resistance structure of black-grass (Alopecurus myosuroides Huds.). One field within a local area, each with confirmed resistance, served as starting point to survey the surrounding fields. Eighty percent of the fields had very few black-grass ears prior to harvest, with mainly ears from single plants spread over the field. Infestation in the other fields was in large patches or widespread, yet in most situations it did not significantly impact on yield level. Resistance to ACCase-inhibiting herbicides was found on all tested fields in each region. Plants with a target-site mutation to ACCase inhibitors were found in all samples; in addition, most plants also exhibited non-target-site resistance. All five mutations conferring ACCase resistance were found. The diversity of the mutations between areas suggests that resistance evolved independently in most fields. At two locations, each one with confirmed ALS resistance, additional fields with reduced ALS efficacy were detected. At one location only the mutation P197T was found, at the second the W574L mutation was also found. Target-site resistance appears to be the major mechanism for these early cases of ALS inhibitor resistance. Understanding the resistance development in individual fields and the spatial dynamics requires investigation over several years. The example of ACCase resistance to black-grass demonstrates how a specific mode of action can be rendered ineffective over a whole region. It provides a possible model for ALS-inhibiting herbicides. In the current situation, farmers are able to manage the black-grass infestation quite well. Resistance in a field seems to develop first in patches with high population densities. Resistance management should therefore focus on the management of the seed bank of each field, using all measures to keep the population pressure low. Keywords: ACCase inhibitors, ALS inhibitors, blackgrass, Germany, non-target-site resistance, target-site resistanceStatus und Entwicklung von ACCase- und ALS-Inhibitor resistenten Ackerfuchsschwanz (Alopecurus myosuroides Huds.) in benachbarten Feldern in DeutschlandBenachbarte Felder aus drei Gebieten in Süddeutschland wurden auf Befall und Struktur von Herbizidresistenzen bei Ackerfuchsschwanz (Alopecurus myosuroides Huds.) untersucht. Jeweils ein Feld mit bestätigter Resistenz diente als Ausgangspunkt für die Untersuchung der umliegenden Felder. Auf 80 Prozent der Felder fanden sich nur sehr wenige Ähren von über das Feld verstreuten Einzelpflanzen. Der Befall auf den anderen Feldern war in größeren Flecken oder über das ganze Feld verteilt, meist ohne geschätzten Einfluss auf den Ertrag. Resistenz zu ACCase-Inhibitoren wurde auf jedem der Felder in jeder Region gefunden. In allen Proben wurden Pflanzen mit Target-Site Mutationen und solche mit Nicht-Target-Site Resistenzen gefunden. Alle fünf bekannten ACCase-Mutationen wurden gefunden. Die große Diversität der Mutationen lässt vermuten, dass sich die Resistenz unabhängig auf den einzelnen Feldern entwickelt hat. In zwei Gebieten gab es von Anfang an jeweils ein Feld mit bestätigter Resistenz gegen ALS-Inhibitoren. Hier wurde auf weiteren Feldern eine reduzierte Herbizidwirkung nachgewiesen. In einer Region wurde die Mutation P197T gefunden, zusätzlich die Mutation W574L auf den Feldern des zweiten Gebiets. Target-site Resistenz scheint die Hauptursache für diese frühe Phase der ALS-Resistenzentwicklung zu sein. Um die Resistenzentwicklung auf einzelnen Feldern und die Ausbreitung über ein ganzes Gebiet zu verstehen, bedarf es Daten mehrerer Jahre. Das Beispiel der Resistenz gegen ACCase Inhibitoren von Ackerfuchsschwanz demonstriert wie ein bestimmter Wirkmechanismus über ein weites Gebiet wirkungslos werden kann. Es ist ein mögliches Model für ALSinhibierende Herbizide. Gegenwärtig wird der Ackerfuchsschwanz in den untersuchten Gebieten von den Landwirten sehr gut bekämpft. Die Resistenzen scheinen sich zuerst auf Feldstellen mit hohen Populationsdichten zu entwickeln. Resistenzmanagement sollte daher an erster Stelle alle möglichen Maßnahmen umfassen, die den Samenvorrat im Boden niedrig halten. Stichwörter: ACCase-Inhibitoren, Ackerfuchsschwanz, ALS-Inhibitoren, Deutschland, Non-Target-Site Resistenz, Target-Site Resisten

On the two-loop contributions to the pion mass

We derive a simplified representation for the pion mass to two loops in three-flavour chiral perturbation theory. For this purpose, we first determine the reduced expressions for the tensorial two-loop 2-point sunset integrals arising in chiral perturbation theory calculations. Making use of those relations, we obtain the expression for the pion mass in terms of the minimal set of master integrals. On the basis of known results for these, we arrive at an explicit analytic representation, up to the contribution from K-K-eta intermediate states where a closed-form expression for the corresponding sunset integral is missing. However, the expansion of this function for a small pion mass leads to a simple representation which yields a very accurate approximation of this contribution. Finally, we also give a discussion of the numerical implications of our results.Comment: Typos corrected and minor changes in Table 2. Published version. 19 pages, 1 figure, 2 table

The bioaccessibility and bioavailability of subsoil phosphorus from P-33-labeled hydroxyapatite

Phosphorus (P) is an essential but often limiting macronutrient in ecosystems. In soil, free phosphorus is rapidly immobilized by sorption onto hydrous oxides or minerals containing Fe, Mn and Al. Therefore plants have the need to increase the availability of P from other sources e.g. solubilizing P from mineral apatite. Apatite can be found in mineral and biological forms, such as residues from bones and dentin, in soil. This Ca-phosphate mineral occurs in trace amounts in practically all metamorphic and igneous rocks and is often found as small mineral inclusions associated to weathering-resistant silicate minerals. Yet, there is not much information on the bioavailability of P from mineral apatite. Numerous papers have been published on hydroxyapatite synthesis, mostly focusing on its use as a bioceramic for biomedical applications that often differ in their physic-chemical properties from mineral apatite. In framework of the DFG-SPP 1685 on ecosystem nutrients the aim of this work was to implement a chemical synthesis for P-33-labeled hydroxyapatite (Ca/P ratio = 1.67) in order to get more information on the bioaccessibility and bioavailability of subsoil P from minerals. A wet-chemical synthesis based on Wang et al. (2010), has been modified and extended, to create a procedure that allows the fast preparation (ca. 30 h) of hydroxyl-apatite labeled with P-33. The products were analyzed with IR-RAMAN and XRD. The reactions were performed under different reaction temperatures which resulted in four forms of hydroxyapatite with different degrees of crystallinity (amorphous high crystalline). Solubility tests were performed with all forms to investigate their pH-dependency, stating that the amorphous and high crystalline forms behave similar but differ from the intermediate forms. Rhizotrone experiments (60 days) will be performed using summer wheat as model organisms and the amorphous apatite form as point sources in soil. Two different subsoils (P-deficient/non-deficient) with two different water scenarios will be used to investigate the differences in root growth and the effects on the bioaccessibility and –availability of P from apatite. Radioactive imaging will be used to get information on the time that the roots need to grow to the apatite source, the amount that is taken up into the plant and to locate the areas of P-storage. High resolution pictures will be taken to investigate the growth of the root system for modeling purposes