Ceramide Analog [\u3csup\u3e18\u3c/sup\u3eF]F-HPA-12 Detects Sphingolipid Disbalance in the Brain of Alzheimer’s Disease Transgenic Mice by Functioning as a Metabolic Probe

The metabolism of ceramides is deregulated in the brain of Alzheimer’s disease (AD) patients and is associated with apolipoprotein (APO) APOE4 and amyloid-β pathology. However, how the ceramide metabolism changes over time in AD, in vivo, remains unknown. Distribution and metabolism of [18F]F-HPA-12, a radio-fluorinated version of the ceramide analog N-(3-hydroxy-1-hydroxymethyl-3-phenylpropyl) dodecanamide, was investigated in the brain of AD transgenic mouse models (FAD) on an APOE4 or APOE3 genetic background, by positron emission tomography and by gamma counter. We found that FAD mice displayed a higher uptake of [18F]F-HPA-12 in the brain, independently from the APOE4 or APOE3 genetic background. FAD mice could be distinguished from littermate control animals with a sensitivity of 85.7% and a specificity of 87.5%, by gamma counter measurements. Metabolic analysis of [18F]F-HPA-12 in the brain suggested that the tracer is degraded less efficiently in the FAD mice. Furthermore, the radioactive signal registered in the hippocampus correlated with an increase of Cer d18:1/20:2 levels measured in the same brain region by mass spectrometry. Our data gives additional proof that ceramide metabolism is different in FAD mice compared to controls. Ceramide analogs like HPA-12 may function as metabolic probes to study ceramide disbalance in the brain

Model complexity and out-of-sample performance: evidence from S&P 500 index returns

We apply a range of out-of-sample specification tests to more than forty competing stochastic volatility models to address how model complexity affects out-of-sample performance. Using daily S&P 500 index returns, model confidence set estimations provide strong evidence that the most important model feature is the non-affinity of the variance process. Despite testing alternative specifications during the turbulent market regime of the global financial crisis of 2008, we find no evidence that either finite- or infinite-activity jump models or other previously proposed model extensions improve the out-of-sample performance further. Applications to Value-at-Risk demonstrate the economic significance of our results. Furthermore, the out-of-sample results suggest that standard jump diffusion models are misspecified

An international multi-center investigation on the accuracy of radionuclide calibrators in nuclear medicine theragnostics

Background: Personalized molecular radiotherapy based on theragnostics requires accurate quantification of the amount of radiopharmaceutical activity administered to patients both in diagnostic and therapeutic applications. This international multi-center study aims to investigate the clinical measurement accuracy of radionuclide calibrators for 7 radionuclides used in theragnostics: 99mTc, 111In, 123I, 124I, 131I, 177Lu, and 90Y. Methods: In total, 32 radionuclide calibrators from 8 hospitals located in the Netherlands, Belgium, and Germany were tested. For each radio

Mutation Detection in Patients with Retinal Dystrophies Using Targeted Next Generation Sequencing

Retinal dystrophies (RD) constitute a group of blinding diseases that are characterized by clinical variability and pronounced genetic heterogeneity. The different nonsyndromic and syndromic forms of RD can be attributed to mutations in more than 200 genes. Consequently, next generation sequencing (NGS) technologies are among the most promising approaches to identify mutations in RD. We screened a large cohort of patients comprising 89 independent cases and families with various subforms of RD applying different NGS platforms. While mutation screening in 50 cases was performed using a RD gene capture panel, 47 cases were analyzed using whole exome sequencing. One family was analyzed using whole genome sequencing. A detection rate of 61% was achieved including mutations in 34 known and two novel RD genes. A total of 69 distinct mutations were identified, including 39 novel mutations. Notably, genetic findings in several families were not consistent with the initial clinical diagnosis. Clinical reassessment resulted in refinement of the clinical diagnosis in some of these families and confirmed the broad clinical spectrum associated with mutations in RD genes

Zelluläre Funktionsstudien zum Wirkungsmechanismus von Shiga Toxinen bei mikro- und makrovaskulären Endothelzelllinien

Bauwens A. Zelluläre Funktionsstudien zum Wirkungsmechanismus von Shiga Toxinen bei mikro- und makrovaskulären Endothelzelllinien. Bielefeld (Germany): Bielefeld University; 2010.Enterohämorrhagische Escherichia coli, die humanpathogene Subgruppe der Shiga Toxin-produzierenden E. coli, verursachen nicht-blutige und blutige Diarrhö, HC und das lebensbedrohliche HUS. HUS resultiert aus der mikrovaskulären Endothelzellschädigung von Nieren, Gehirn und anderen Organen. Stx, die Hauptvirulenzfaktoren der EHEC, bestehen aus einer enzymatisch aktiven A-Untereinheit und fünf identischen B-Untereinheiten. Die Familie der Stx umfasst zwei Hauptgruppen, Stx1 und Stx2, welche 53 bzw. 64 Prozent Sequenzidentität in ihrer A- bzw. B-Untereinheit aufweisen. Nach der Freisetzung der Stx durch die EHEC im Lumen des Gastrointestinaltraktes gelangen diese über den Blutkreislauf zu ihrem Wirkungsort, den kapillaren Endothelzellen. Dort binden die Toxine an die zellulären Rezeptoren, werden internalisiert und intrazellulär retrograd prozessiert. Im Zytosol wirkt das katalytisch aktive A1-Fragment durch spezifische Depurinierung von Adenosin der hochkonservierten 60S-rRNA toxisch. Dies führt zur Inhibition der Proteinbiosynthese und zum Zelltod. Neben diesem zytotoxischen Effekt wurden weitere Wirkungen von Stx auf Zellen beschrieben, beispielsweise die Depurinierung von chromosomaler DNA, die Umorganisation des Zytoskelettes und die Induktion von Apoptose. Im Rahmen dieser Dissertation wurden die zytotoxischen Effekte von Stx1 und Stx2 auf humane mikro- und makrovaskuläre Endothelzellen untersucht. Mit Hilfe von Zellproliferations- und Zytotoxizitätsassays konnten konzentrationsabhängig unterschiedliche Sensitivitäten der beiden Zelllinien gegenüber den Toxinen festgestellt werden. Hierbei konnte gezeigt werden, dass mikrovaskuläre im Vergleich zu makrovaskulären Zellen besonders sensitiv auf Stx2 reagieren. Dies deckt sich mit den Beobachtungen der zerebralen Schädigung im Patienten, da meist solche EHEC-Stämme mit schweren klinischen Verläufen assoziiert werden können, die Stx2 produzieren. Um einen genaueren Einblick in die Mechanismen der Zytotoxizität zu erlangen, wurden SEM-Aufnahmen von konfluenten Zellmonolayern auf MC vor und nach Toxinbehandlung angefertigt. Während Stx1 eine Verringerung der Anzahl von Mikrovilli-Strukturen auf der Zelloberfläche, irreguläre Zellformen, Läsionen der Plasmamembran, Ausbildung von Membrankörperchen (das sog. blebbing) und Lücken im Zellmonolayer durch Zellablösung verursacht, sind nach Inkubation mit Stx2 lediglich eine leicht veränderte Form der Zellen sowie blebbing zu beobachten. Diese morphologischen Untersuchungen, insbesondere das Ausbleiben von nekrotischen Effekten wie Membranläsionen oder Zellablösung in Stx2-behandelten Endothelzellen, führten zu der Hypothese, dass Stx1 sowohl Nekrose als auch Apoptose, Stx2 hingegen hauptsächlich Apoptose induziert. Zur Verifizierung dieser verschiedenen Mechanismen wurde eine Methode basierend auf DHM etabliert, um HBMECs und EA.hy 926 Zellen einer Einzelzell-Analyse zu unterziehen. Die Visualisierung der Nekrose nach Inkubation mit Stx1 zu unterschiedlichen Zeitpunkten bestätigt die differentielle Sensitivität mikro- und makrovaskulärer Endothelzellen. Zusätzlich lässt sich der Prozess der Nekrose dreidimensional quantifizieren. Bei Experimenten mit Stx2 konnte keine Nekrose beobachtet werden, allerdings auch keine Zellteilung trotz einer verlängerten Experimentaldauer. Um einen durch Stx verursachten Zellzyklus-Arrest auszuschließen, wurden Zellzyklusstudien mit Hilfe der Durchflusszytometrie durchgeführt. Da kein signifikanter Zellzyklus-Arrest durch Stx verursacht wird, muss die Teilungsinaktivität der Zellen auf einer Induktion der Apoptose durch Stx2 beruhen. Dies konnte mittels DNA-Fragmentierungsassays bestätigt und die Effekte konzentrationsabhängig quantifiziert werden. Da die in dieser Arbeit untersuchten differentiellen Effekte von Stx1 und Stx2 nicht auf die bisher beschriebenen Wirkungsweisen von Stx zurückzuführen sind, muss angenommen werden, dass hier ein oder mehrere bisher unbeschriebene Mechanismen zugrunde liegen. Des Weiteren wurde die Inhomogenität von HBMECs und EA.hy 926 Zellen in Kultur mit DHM, IF und Durchflusszytometrie untersucht. Dabei konnten variierende nekrotische Todeszeitpunkte der Zellen beobachtet und die Frage negiert werden, ob die Menge des Zelloberflächen-assoziierten Rezeptors mit der Empfindlichkeit der Zellen gegenüber Stx in Zusammenhang steht. Zudem wurde gezeigt, dass die Expression von Gb3Cer nicht Zellzyklus-abhängig ist. Die in dieser Dissertation entwickelten Methoden wurden zudem eingesetzt, um einen weiteren Virulenzfaktor der EHEC, EHEC-Vac, zu charakterisieren. Die Verwendung der IF zeigte, dass die EHEC-Vac-bedingten Vakuolen lysosomalen Ursprungs sind. Final war die Inkubation der Zellen mit EHEC-Vac letal. Die Art des Zelltodes und Hinweise auf die Dynamik der Vakuolenbildung konnten mit Langzeitmessungen im DHM bestimmt werden

Towards a political ecology of the digital economy : Socio-environmental implications of two competing value models

This article explores the socio-environmental implications of two different value models currently competing for dominance in the digital economy: the neo-feudal cognitive capitalism (NFCC) and the hypothetical case of mature peer production (HMPP). Using a systematisation that considers environmental effects of information and communication technologies as direct, indirect and structural, this article discerns the future socio-environmental scenarios indicative of each value model. We argue that the two value models share the same type of direct environmental effects associated with a similar technological infrastructure; however, their indirect effects differ in prospects of consumer behaviour, environmental awareness and product design. Likewise the difference in structural effects is significant as the NFCC is based on profit maximisation and an accumulation of capital, whereas the HMPP is agnostic to growth and oriented towards the commons. Hence, the latter is considered as the socio-environmentally auspicious choice, but comes not without transitional challenges of its ow

Characterisation of the Escherichia coli strain associated with an outbreak of haemolytic uraemic syndrome in Germany, 2011: a microbiological study

Background: In an ongoing outbreak of haemolytic uraemic syndrome and bloody diarrhoea caused by a virulent Escherichia coli strain O104:H4 in Germany (with some cases elsewhere in Europe and North America), 810 cases of the syndrome and 39 deaths have occurred since the beginning of May, 2011. We analysed virulence profiles and relevant phenotypes of outbreak isolates recovered in our laboratory. Methods: We analysed stool samples from 80 patients that had been submitted to the National Consulting Laboratory for Haemolytic Uraemic Syndrome in Münster, Germany, between May 23 and June 2, 2011. Isolates were screened with standard PCR for virulence genes of Shiga-toxin-producing E coli and a newly developed multiplex PCR for characteristic features of the outbreak strain (rfbO104, fliCH4, stx2, and terD). Virulence profiles of the isolates were determined with PCR targeting typical virulence genes of Shiga-toxin-producing E coli and of other intestinal pathogenic E coli. We sequenced stx with Sanger sequencing and measured Shiga-toxin production, adherence to epithelial cells, and determined phylogeny and antimicrobial susceptibility. Findings: All isolates were of the HUSEC041 clone (sequence type 678). All shared virulence profiles combining typical Shiga-toxin-producing E coli (stx2, iha, lpfO26, lpfO113) and enteroaggregative E coli (aggA, aggR, set1, pic, aap) loci and expressed phenotypes that define Shiga-toxin-producing E coli and enteroaggregative E coli, including production of Shiga toxing 2 and aggregative adherence to epithelial cells. Isolates additionally displayed an extended-spectrum β-lactamase phenotype absent in HUSEC041. Interpretation: Augmented adherence of the strain to intestinal epithelium might facilitate systemic absorption of Shiga toxin and could explain the high progression to haemolytic uraemic syndrome. This outbreak demonstrates that blended virulence profiles in enteric pathogens, introduced into susceptible populations, can have extreme consequences for infected people

Brown adipose tissue uptake of triglyceride-rich lipoprotein-derived fatty acids in diabetic or obese mice under different temperature conditions

Background In vivo imaging of glucose analogue 2-deoxy-2-[F-18]fluoro-d-glucose ([F-18]FDG) via positron emission tomography (PET) is the current gold standard to visualize and assess brown adipose tissue (BAT) activity. However, glucose metabolism is only a part of the metabolic activity of BAT. [F-18]FDG-PET has been shown in clinical trials to often fail to visualize BAT under insulin-resistant conditions associated with aging and weight gain. We employed a novel developed triglyceride-based tracer to visualize BATs metabolic activity under different temperature conditions as well as under diabetic and obese conditions in preclinical models. Results [F-18]BDP-TG-chylomicron-like particles visualized BAT in control, streptozocin-induced diabetes and obese mice. Increased BAT tracer uptake was found in control mice acutely exposed to cold but not in cold-acclimated animals. Diabetes did not remove BAT tracer uptake, but did limit BAT tracer uptake to levels of control mice housed at 21 degrees C. In obese animals, BAT tracer uptake was significantly reduced, although the stimulating effect of cold exposure could still be noted. Conclusion BAT was visualized in control, diabetic and obese conditions. Streptozocin-induced diabetes, but not obesity, inhibited the stimulatory effect of cold exposure

Determination of virulence and fitness genes associated with the pheU, pheV and selC integration sites of LEE-negative food-borne Shiga toxin-producing Escherichia coli strains

Abstract Background In the current study, nine foodborne “Locus of Enterocyte Effacement” (LEE)-negative Shiga toxin-producing Escherichia coli (STEC) strains were selected for whole genome sequencing and analysis for yet unknown genetic elements within the already known LEE integration sites selC, pheU and pheV. Foreign DNA ranging in size from 3.4 to 57 kbp was detected and further analyzed. Five STEC strains contained an insertion of foreign DNA adjacent to the selC tRNA gene and five and seven strains contained foreign DNA adjacent to the pheU and pheV tRNA genes, respectively. We characterized the foreign DNA insertion associated with selC (STEC O91:H21 strain 17584/1), pheU (STEC O8:H4 strain RF1a and O55:Hnt strain K30) and pheV (STEC O91:H21 strain 17584/1 and O113:H21 strain TS18/08) as examples. Results In total, 293 open reading frames partially encoding putative virulence factors such as TonB-dependent receptors, DNA helicases, a hemolysin activator protein precursor, antigen 43, anti-restriction protein KlcA, ShiA, and phosphoethanolamine transferases were detected. A virulence type IV toxin-antitoxin system was detected in three strains. Additionally, the ato system was found in one strain. In strain 17584/1 we were able to define a new genomic island which we designated GIselC 17584/1. The island contained integrases and mobile elements in addition to genes for increased fitness and those playing a putative role in pathogenicity. Conclusion The data presented highlight the important role of the three tRNAs selC, pheU, and pheV for the genomic flexibility of E. coli