Microtubule stabilization specifies initial neuronal polarization

Axon formation is the initial step in establishing neuronal polarity. We examine here the role of microtubule dynamics in neuronal polarization using hippocampal neurons in culture. We see increased microtubule stability along the shaft in a single neurite before axon formation and in the axon of morphologically polarized cells. Loss of polarity or formation of multiple axons after manipulation of neuronal polarity regulators, synapses of amphids defective (SAD) kinases, and glycogen synthase kinase-3β correlates with characteristic changes in microtubule turnover. Consistently, changing the microtubule dynamics is sufficient to alter neuronal polarization. Application of low doses of the microtubule-destabilizing drug nocodazole selectively reduces the formation of future dendrites. Conversely, low doses of the microtubule-stabilizing drug taxol shift polymerizing microtubules from neurite shafts to process tips and lead to the formation of multiple axons. Finally, local stabilization of microtubules using a photoactivatable analogue of taxol induces axon formation from the activated area. Thus, local microtubule stabilization in one neurite is a physiological signal specifying neuronal polarization

Bewertung von pharmakokinetischen Parametern zur Phänotypisierung des menschlichen Cytochrom P450 Enzyms CYP2D6 mittels Dextromethorphan

Der Umsatz von Dextromethorphan (DEX) zu dessen CYP2D6 abhängig gebildeten Metaboliten Dextrorphan (DOR) wird seit langer Zeit für die CYP2D6 Phänotypisierung verwendet, jedoch fehlt es bislang an einer systematischen Validierung der hierfür einsetzbaren Phänotypisierungsparameter. Daher war das Ziel dieser Dissertation die Evaluierung von 48 möglichen Parametern in Urin und Plasma anhand definierter Validierungskriterien. Für diese Arbeit wurden 84 Probanden und Patienten in fünf Cocktail-Interaktionsstudien je zweimal mit DEX phänotypisiert. Zur Analyse der hierbei gewonnenen Plasma- und Urinproben wurde eine robuste, sensitive und selektive LC-MS/MS Methode entwickelt und validiert. Die Proben wurden jeweils mit und ohne Spaltung der DOR-Glucuronide vermessen, um beide Verfahren bezüglich ihrer Eignung zu vergleichen. Die Validierung aller Parameter erfolgte zunächst durch Berechnung der jeweiligen inter- und intraindividuellen Variationskoeffizienten (CV inter/intra) sowie durch Korrelation mit Vergleichsparametern, welche die CYP2D6 Aktivität zuverlässig widerspiegeln. Zur Verifizierung der Phänotypisierungsdaten wurden 48 Probanden auf 26 verschiedene CYP2D6 Allele hin genotypisiert und entsprechend der dem Genotyp nach zu erwartenden Enzymaktivität in ein activity-score System (AS) eingeteilt. Der Zusammenhang zwischen Genotyp-AS und Phänotyp wurde graphisch und mittels einfaktorieller ANOVA rechnerisch überprüft. Für viel versprechende Parameter erfolgte eine weitere Validierung durch lineare Regression zwischen Genotyp-AS und Phänotyp und durch getrennt nach Genotyp-AS durchgeführte Berechnung des CV intra. Zur besseren Vergleichbarkeit der Ergebnisse wurde ein Punkte-Scoringsystem entwickelt, anhand dessen die Validierungsergebnisse für alle Parameter in vergleichbare Zahlenwerte überführt werden konnten. Bestimmungen in Urin ergaben insgesamt höhere CV intra Ergebnisse und schlechtere Zusammenhänge zwischen Genotyp-AS und Phänotyp, zudem spielt hier als Fehlerquelle der Urin pH hinein, was durch lineare Regression der DEX-/DOR-Clearance mit dem Urin pH nachgewiesen wurde. Die Methode der Deglucuronidierung ergab für Messungen in Plasma und Urin weniger Scoringpunkte im Vergleich zu nicht behandelten Proben. Hier erzielten die Plasmaproben zwischen 2 h und 4h15 die besten Scoringergebnisse, zunächst in den grundlegenden Validierungsschritten und ebenso in den zusätzlichen beiden Schritten. Somit ergibt sich ein klarer Vorteil einer Phänotypisierung mit Plasmaparametern, wobei das metabolische Verhältnis in 3h15 Plasma die höchste Scoring-Punktzahl erzielte, so dass sich dieser Parameter als validestes Maß für die CYP2D6 Phänotypisierung feststellen lässt.Evaluation of pharmacokinetic metrics for phenotyping of the human CYP2D6 enzyme with dextromethorphan The conversion of dextromethorphan (DEX) to its CYP2D6 mediated metabolite dextrorphan (DOR) has been used for CYP2D6 phenotyping for decades, however, the utability of the different possible phenotyping tools needs further validation. In this work 48 different phenotyping metrics in urine and plasma were validated systematically according to pre-defined validation criteria. 84 subjects, who took part in five cocktail-interaction trials, were phenotyped with DEX twice. For the analytics of the thereby obtained plasma and urine samples a robust, sensitive, and selective LC MS/MS method was developed and validated first. The samples were analysed first with and then without cleavage of the DOR-glucuronides respectively. Validation of each possible phenotyping-metric was carried out by calculation of inter- and intraindividual coefficients of variation (CV inter/intra). Furthermore, correlations of all metrics with comparative parameters, which are known to exactly reflect CYP2D6 activity, were evaluated. The phenotying results were verified by vast genotyping experiments including 26 CYP2D6 alleles for 48 subjects, and the obtained data were then classified to seven activity-score (AS) sub-groups according to the enzymatic activity expected from the genotyping data. The relations between genotype-AS and phenotype were examined by graphical plots and by one-way ANOVA. The most promising metrics were additionally validated by linear regression between AS-groups and phenotyping results as well as by separate calculation of inter- and intraindividual coefficients of variation for each AS-group. To allow better comparability of all evaluated metrics, the validation results were converted into numerical values according to a scoring-system. Urine phenotyping gave higher CV intra results and worse relations between genotype-AS and phenotype. Additionally, measurements in urine are influenced by urine-pH, which was proved by linear regression between drug clearance and pH for both analytes. Glucuronide-cleavage gave worse scoring-results for both plasma and urine phenotyping in comparison to untreated samples. Regarding the plasma metrics without deglucuronidation the best accordance with all validation criteria was reached for samples taken between 2 h and 4h15. This was first shown by the basic four validation steps and was then confirmed by two additional steps. A clear advantage of plasma-phenotyping was revealed, while the metabolic ratio DEX/DOR of the 3h15 sample attained the highest scoring-results in particular. Thus, this phenotyping metric is designated the most appropriate tool for CYP2D6 phenotyping according to the thorough validation carried out in this work

Konstruktion eines Testinstruments zur Erhebung des Professionswissens von Lehramtsstudierenden im Fach Sozialwissenschaften (SoWis-L)

In diesem Beitrag wird die Konstruktion und Validierung eines Testinstruments zur Erhebung des Professionswissens von angehenden Lehrkräften im Fach Sozialwissenschaften (SoWi) vorgestellt. Der SoWis-L ("Sozialwissenschaftliches Wissen - Lehrkräfte") stellt für das Lehramtsstudienfach SoWi das erste standardisierte Testinstrument zur ökonomischen Erhebung von Professionswissen unter Berücksichtigung des Integrationsfachcharakters dar. Anhand einer Stichprobe von N = 374 Lehramtsstudierenden der Universität Duisburg-Essen (UDE) wurde das 46-Item-Instrument bezüglich seiner Testgüte untersucht. IRT-Analysen ergaben zufriedenstellende Reliabilitäts- und Itemfitwerte für alle Wissensbereiche mit Ausnahme des soziologischen Fachwissens. Strukturanalysen sprechen für eine dreidimensionale Modellierung mit einer fachdidaktischen Wissensdimension und zwei fachwissenschaftlichen Dimensionen (politisches und wirtschaftliches Wissen). Die Kriteriumsvalidität des Instruments ist mit signifikanten Gruppenunterschieden zwischen Bachelor- und Masterstudierenden, zwischen gymnasialen und nicht-gymnasialen Lehrämtern sowie einer signifikanten Korrelation mit Abiturnoten indiziert.This article presents a standardized test measuring the pedagogical content knowledge (PCK) and content knowledge (CK) of social science teacher students. The SoWis-L ("Sozialwissenschaftliches Wissen - Lehrkräfte," Engl.: Professional Knowledge of Social Science Teachers) covers declarative and conceptual knowledge from three knowledge domains. The 46-item instrument was developed and validated based on a sample of N = 374 social science teacher students. We examined research questions concerning psychometric test criteria, especially reliability and criterion validity. IRT analyses showed good item fit and adequate reliability for all knowledge areas except sociological content knowledge. A structural equation model resulted in a good fit of the model with three correlated latent factors, i. e., PCK and two facets of CK (political and economic CK). A comparison of the test results in teacher students aiming at a grammar school vs. a nongrammar school teaching degree and those enrolled in master vs. bachelor studies as well as significant correlations with grades in final school exams ("Abitur") indicate the criterion validity of the SoWis-L

Integration von Wasserstoffenergiespeichern - Nutzen für Stromnetze?

Der Beitrag gibt einen Überblick über die Anforderungen an eine netzorientierte Integration von Wasserstoffenergiespeichern und -komponenten in das Stromnetz. Vor dem Hintergrund einer allgemeinen Definition von Wasserstoffenergiespeichern und möglichen Komponenten werden der zukünftige Wasserstoffbedarf, Elektrolyseleistung und Speicherkapazität vorgestellt, der in verschiedenen aktuellen Gesamtsystemstudien mit Ziel der Klimaneutralität im Jahr 2045 bestimmt wurde. Durch den angestrebten beschleunigten Ausbau erneuerbarer Erzeugungskapazität ergibt sich weiterer Netzausbaubedarf zusätzlich zu dem Ausbaubedarf durch bisherige Netzengpässen. Elektrolyseanlagen könnten also bereits im heutigen Stromnetz zur verbesserten Integration von EE-Anlagen eingesetzt werden. Derzeit bestehen allerdings kaum Anreize für netzdienliche Allokation und Betrieb von Elektrolyse bzw. Power-to-Gas Anlagen. Als Praxisbeispiele werden zwei mögliche Standorte für Wasserstoffanlagen aus zwei aktuellen Forschungsprojekten HyCavMobil und dem Innovationslabor Wasserstoffregion Nordwest (H2-ReNoWe) vorgestellt. Anhand von Stromnetzmodellen wird die Integration von Elektrolyseanlagen an diesen Standorten im derzeitigen Hoch- bzw. Höchstspannungsnetz untersucht

Stability of the timing of food intake at daily and monthly timescales in young adults

Cross-sectional observations have shown that the timing of eating may be important for health-related outcomes. Here we examined the stability of eating timing, using both clock hour and relative circadian time, across one semester (n = 14) at daily and monthly time-scales. At three time points ~ 1 month apart, circadian phase was determined during an overnight in-laboratory visit and eating was photographically recorded for one week to assess timing and composition. Day-to-day stability was measured using the Composite Phase Deviation (deviation from a perfectly regular pattern) and intraclass correlation coefficients (ICC) were used to determine individual stability across months (weekly average compared across months). Day-to-day clock timing of caloric events had poor stability within individuals (~ 3-h variation; ICC = 0.12–0.34). The timing of eating was stable across months (~ 1-h variation, ICCs ranging from 0.54–0.63), but less stable across months when measured relative to circadian timing (ICC = 0.33–0.41). Our findings suggest that though day-to-day variability in the timing of eating has poor stability, the timing of eating measured for a week is stable across months within individuals. This indicates two relevant timescales: a monthly timescale with more stability in eating timing than a daily timescale. Thus, a single day’s food documentation may not represent habitual (longer timescale) patterns

Ultrasound-induced release of nimodipine from drug-loaded block copolymer micelles: in vivo analysis

Nimodipine prevents cerebral vasospasm and improves functional outcome after aneurysmal subarachnoid hemorrhage (aSAH). The beneficial effect is limited by low oral bioavailability of nimodipine, which resulted in an increasing use of nanocarriers with sustained intrathecal drug release in order to overcome this limitation. However, this approach facilitates only a continuous and not an on-demand nimodipine release during the peak time of vasospasm development. In this study, we aimed to assess the concept of controlled drug release from nimodipine-loaded copolymers by ultrasound application in the chicken chorioallantoic membrane (CAM) model. Nimodipine-loaded copolymers were produced with the direct dissolution method. Vasospasm of the CAM vessels was induced by means of ultrasound (Physiomed, continuous wave, 3 MHz, 1.0 W/cm(2)). The ultrasound-mediated nimodipine release (Physiomed, continuous wave, 1 MHz, 1.7 W/cm(2)) and its effect on the CAM vessels were evaluated. Measurements of vessel diameter before and after ultrasound-induced nimodipine release were performed using ImageJ. The CAM model could be successfully carried out in all 25 eggs. After vasospasm induction and before drug release, the mean vessel diameter was at 57% (range 44–61%) compared to the baseline diameter (set at 100%). After ultrasound-induced drug release, the mean vessel diameter of spastic vessels increased again to 89% (range 83–91%) of their baseline diameter, which was significant (p = 0.0002). We were able to provide a proof of concept for in vivo vasospasm induction by ultrasound application in the CAM model and subsequent resolution by ultrasound-mediated nimodipine release from nanocarriers. This concept merits further evaluation in a rat SAH model. GRAPHICAL ABSTRACT: [Image: see text

Review of Hydrogen Production Techniques from Water Using Renewable Energy Sources and Its Storage in Salt Caverns

Hydrogen is becoming an increasingly important energy carrier in sector integration for fuel cell transportation, heat and electricity. Underground salt caverns are one of the most promising ways to store the hydrogen obtained from water electrolysis using power generation from renewable energy sources (RES). At the same time, the production of hydrogen can be used to avoid energy curtailments during times of low electricity demand or low prices. The stored hydrogen can also be used during times of high energy demand for power generation, e.g., with fuel cells, to cover the fluctuations and shortages caused by low RES generation. This article presents an overview of the techniques that were used and proposed for using excess energy from RES for hydrogen production from water and its storage techniques, especially in underground salt caverns, for the aforementioned purpose, and its feasibility. This paper compares and summarizes the competing technologies based on the current state-of-the-art, identifies some of the difficulties in hydrogen production and storage, and discusses which technology is the most promising. The related analysis compares cost and techno-economic feasibility with regard to hydrogen production and storage systems. The paper also identifies the potential, technical challenges and the limitations associated with hydrogen integration into the power grid

Mobile Genetic Element-Encoded Cytolysin Connects Virulence to Methicillin Resistance in MRSA

Bacterial virulence and antibiotic resistance have a significant influence on disease severity and treatment options during bacterial infections. Frequently, the underlying genetic determinants are encoded on mobile genetic elements (MGEs). In the leading human pathogen Staphylococcus aureus, MGEs that contain antibiotic resistance genes commonly do not contain genes for virulence determinants. The phenol-soluble modulins (PSMs) are staphylococcal cytolytic toxins with a crucial role in immune evasion. While all known PSMs are core genome-encoded, we here describe a previously unidentified psm gene, psm-mec, within the staphylococcal methicillin resistance-encoding MGE SCCmec. PSM-mec was strongly expressed in many strains and showed the physico-chemical, pro-inflammatory, and cytolytic characteristics typical of PSMs. Notably, in an S. aureus strain with low production of core genome-encoded PSMs, expression of PSM-mec had a significant impact on immune evasion and disease. In addition to providing high-level resistance to methicillin, acquisition of SCCmec elements encoding PSM-mec by horizontal gene transfer may therefore contribute to staphylococcal virulence by substituting for the lack of expression of core genome-encoded PSMs. Thus, our study reveals a previously unknown role of methicillin resistance clusters in staphylococcal pathogenesis and shows that important virulence and antibiotic resistance determinants may be combined in staphylococcal MGEs

The Nature and Conceptualisation of Career Transitions in Sport

First paragraph: While an athlete’s sports career may seem to develop in a smooth and continuous way from beginning to end, it is in fact characterized by specific phases and transitions. Asked to describe its development, athletes highlight their athletic career, for example, in terms of specific moments or situations which occurred throughout their career (Wylleman & De Knop, 1997a,b). These moments or situations do not only require athletes to cope with specific changes, but are also perceived by the athletes to influence the quality of their participation at their current competitive level. The occurrence of phases and transitions in the athletic career can also be illustrated by chronologically pin-pointing athletes’ sport achievements (e.g., a first national championship title) and selections (e.g., selection for the national team). Comparison of such developmental data has revealed many similarities in (elite) athletes’ athletic careers (Stambulova, 1998; Wylleman & De Knop, 1998): athletes start out in their sport at the ages of approximately 8 to 12 years-of-age; one or two years later athletes start competing at club level, and go, some three to four years later on to national level; a first selection for a national team occurs somewhere between 17-19 years-of-age, while a first Olympic selection is achieved during their early twenties; and finally, athletes do end their involvement in highlevel competitive sport at approximately 30 years-of-age (3). In fact, researchers have been able to identify a sequence of career developmental phases, not only with elite level athletes, but with talented performers in general, namely an initiation, a development, a mastery, and a post-career phase (e.g., Bloom, 1985; Salmela; 1994)