Tissue distribution of 5-hydroxymethylcytosine and search for active demethylation intermediates.

5-Hydroxymethylcytosine (hmC) was recently detected as the sixth base in mammalian tissue at so far controversial levels. The function of the modified base is currently unknown, but it is certain that the base is generated from 5-methylcytosine (mC). This fuels the hypothesis that it represents an intermediate of an active demethylation process, which could involve further oxidation of the hydroxymethyl group to a formyl or carboxyl group followed by either deformylation or decarboxylation. Here, we use an ultra-sensitive and accurate isotope based LC-MS method to precisely determine the levels of hmC in various mouse tissues and we searched for 5-formylcytosine (fC), 5-carboxylcytosine (caC), and 5-hydroxymethyluracil (hmU) as putative active demethylation intermediates. Our data suggest that an active oxidative mC demethylation pathway is unlikely to occur. Additionally, we show using HPLC-MS analysis and immunohistochemistry that hmC is present in all tissues and cell types with highest concentrations in neuronal cells of the CNS

Gefäßveränderungen nach intrauteriner Wachstumsretardierung

Children with intrauterine growth retardation more often develop a diabetes, hypertension and hyperlipidemia later in life. Some evidence exists that Children with IUGR also have higher risk to develop atherosclerosis. In this study, we aimed to clarify the contribution of IUGR to the developement of vascular injury in an animal model of IUGR. Furthermore, we studied the effects of IUGR on the developement of atheroclerotic lesions. The increased expression of some matrix components in vessels after IUGR may result in an altered composition of the vascular wall, which could negatively influence vascular compliance. This might render blood vessels more susceptible to injury. The fact that these vascular changes occur early and long befor hypertension can be observed, argue for a direct contribution of IUGR to vascular damage which acts independently from other risk factors for the developement of atherosclerosis.Kinder mit intrauteriner Wachstumsretardierung erkranken im späteren Leben häufiger an D.m. II, Hyperlipidämie und Hypertonie. Auch gibt es Hinweise auf eine verstärkte Atheroskleroseneigung. In dieser Arbeit sollte in einem Tiermodell der IUGR untersucht werden, in wie weit die IUGR für die Entwicklung späterer Gefäßschäden prädestiniert und ob sie einen Einfluss auf die Entwicklung atherosklerotischer Gefäßveränderungen hat. Die verstärkte Expression einiger Matrixmoleküle in Gefäßen nach IUGR führt sehr wahrscheinlich zu einer veränderten Zusammensetzung der Gefäßwand, die sich auf die Compliance negativ auswirken könnte und in der Folge die Gefäße anfälliger für Schädigungen macht. Die Tatsache, dass diese Gefäßveränderungen schon früh und vor dem Auftreten von Hypertonie auftreten, lässt darauf schliessen, dass IUGR, unabhängig von anderen Risikofaktoren, direkt Gefäßveränderungen induziert, die eine Atheroskleroseentstehung begünstigen

Superficies que engañan: dos experiencias

Two fieldwork experiences are compared here. At a first glance they seem to be quite different: On the one side, a traditionalist society is defending its culture and does not take the anthropologist for important. On the other side, a community depending on non-indigenous merchants respects the anthropologist as one more of those mighty invaders with whom you better cooperate. But in both cases, at the end the anthropologist must admit that he had not understood the situation. Under the surface of the differences, he discovers parallels. At a second glance, the indigenous society apparently dependent proves to be quite strong. And this is the anthropologist’s profession: To understand the apparent and the occult of a society we visit, to the degree up to which this society decides to admit our understanding.Se comparan dos experiencias de trabajo de campo que a primera vista parecen muy diferentes: Por un lado, una sociedad tradicionalista que defiende su cultura y no da mucha importancia al antropólogo. Por otro lado, una comunidad dependiente de comerciantes no indígenas y que considera al antropólogo como otro invasor representante de la sociedad nacional poderosa con el que hay que colaborar. En los dos casos, el antropólogo al final debe admitir que no había comprendido muy bien la situación: debajo de las diferencias, descubre paralelos. La sociedad indígena a primera vista destruida y dependiente, a segunda vista se mantiene muy fuerte. Y es una esencia del trabajo antropológico: comprender lo aparente y lo oculto en la medida en que la sociedad a la que se visita quieran bien dejarnos comprender

Takotsubo Syndrome: Impact of endothelial dysfunction and oxidative stress

Takotsubo Syndrome (TTS) is characterized by a transient left ventricular dysfunction recovering spontaneously within days or weeks. Although the pathophysiology of TTS remains obscure, there is growing evidence suggesting TTS to be associated with increased production of reactive oxygen species (ROS), which may be involved in causing transient coronary and peripheral endothelial dysfunction leading to a transient impairment of myocardial contraction due to stunning (apical ballooning). Endothelial dysfunction is mainly caused by decreased vascular and myocardial nitric oxide bioavailability in response to increased ROS production. Accordingly, studies in humans and animal models demonstrated increased myocardial dihydroethidium staining of the myocardium in endomyocardial biopsy specimens, increased levels of hydrogen peroxide and malondialdehyde as well as reduced glutathione levels compatible with increased oxidative stress. As significant superoxide sources the mitochondria and the NADPH oxidase isoform NOX-4 and the NOX-2 regulating cytosolic subunit p67phox have been identified. Treatment with antioxidants such as sodium hydrosulfide reduced superoxide production in mitochondria and reduced expression of NOX-4 and p67phox, respectively. The presence of superoxide and nitric oxide also provides the basis for the concept of nitro-oxidative as well as nitrosative stress in TTS

Spin-Waves in the Mid-Infrared Spectrum of Antiferromagnetic YBa2_2Cu3_3O6.0_{6.0}

The mid-infrared spin-wave spectrum of antiferromagnetic YBa$_2$Cu$_3$O$_{6.0}$\ was determined by infrared transmission and reflection measurements (\bbox{k} \!\! \parallel c) at $T\!=\!10\!$~K.\@ Excitation of single magnons of the optical branch was observed at $E_{\text{op}}\!=\!178.0\!$~meV.\@ Two further peaks at $346\!$~meV ($\approx\!1.94\,E_{\text{op}}$) and $470\!$~meV ($\approx\!2.6\,E_{\text{op}}$) both belong to the two-magnon spectrum. Linear spin wave theory is in good agreement with the measured two-magnon spectrum, and allows to determine the exchange constant $J$ to be about $120\!$~meV, whereas the intrabilayer coupling $J_{12}$ is approximately $0.55\,J$.Comment: 3 figures in uuencoded for

Investigating myelination and remyelination in zebrafish

Central nervous system (CNS) myelination is important for proper nervous system function in vertebrates. In demyelinating diseases such as multiple sclerosis, autoimmune-mediated myelin destruction results in neurological impairment; and although remyelination does occur spontaneously, it is poorly understood and insufficient in humans. Zebrafish (Danio rerio) are known to harbour tremendous regenerative capacity of various CNS tissues; however, there is presently only little knowledge of their myelin repair efficiency. An experimental model of myelin injury in zebrafish would permit study of the mechanisms involved in successful remyelination and could potentially guide the development of novel therapeutic agents for mammalian remyelination. This doctoral thesis describes the characterisation of the novel myelin protein Claudin k in zebrafish, demonstrates the establishment of adult zebrafish as an experimental model for CNS de- and remyelination and explores some mechanisms underlying myelin repair. A variety of myelin markers have previously been investigated in zebrafish, including myelin basic protein and myelin protein zero. However, the use of these is limited by either late developmental expression or presence in compact myelin only. Claudin k is a novel tight junction protein specific to zebrafish CNS and PNS, which can be observed early in development and throughout nervous system regeneration. Utilising specific antibodies and a novel transgenic zebrafish line, in which the claudin k promoter drives the expression of green fluorescent protein in myelinating cells, the studies herein characterise the expression of Claudin k, demonstrate the fidelity of the transgenic construct, and investigate the relationship of Claudin k with established myelin and CNS inflammation markers. Data demonstrate that Claudin k expression closely resembles expression patterns of the endogenous gene, and as such provides a key tool for examining CNS myelination in zebrafish. For the study of de- and remyelination in the zebrafish, the experiments herein describe the use of lysophosphatidylcholine (LPC), a detergent-like myelin toxin, which is used widely in rodent models to demyelinate axons. Its application to the adult zebrafish optic nerve induced focal demyelinating lesions, critically without detectable axonal injury, and permitted the study of time course and efficiency of remyelination. Myelin in the lesion area was reduced as detected by both immunohistochemistry and electron microscopy at 8 days post lesion (dpl), and return of the markers to control levels suggested regeneration by 28 dpl. In addition microglial activation was observed along the optic pathway, which also returned to levels compared to unlesioned control by 28 dpl. In young zebrafish (aged 4-6 months), the myelin thickness of remyelinated fibres showed no difference to the pre-lesion state, which is different to mammals, where the myelin thickness is reduced. However, in old fish (aged 18+ months), remyelinated fibres presented with thinner myelin, suggesting that the regenerative capacity of zebrafish declines with age. While the zebrafish as an experimental system has tremendous benefits, such as potential for drug screens using the transparent larvae, capacity for transgenesis and live imaging, experimental models in zebrafish potentially bear several limitations, in particular their distant relationship to humans. To determine whether zebrafish remyelination involves homologous signalling mechanisms to mammals, demyelinated zebrafish optic nerves were treated with human recombinant Semaphorin 3A, an axonal guidance molecule which is well known to inhibit oligodendrocyte precursor cell (OPC) recruitment and remyelination in mammals. Results demonstrated fewer oligodendroglial cells at 14 dpl and less myelinated fibres at 28 dpl in the optic nerve lesion area compared to control treated animals, supporting the hypothesis that zebrafish remyelination may indeed respond to human signalling molecules. Taken together, the findings in this doctoral thesis suggest that this new experimental zebrafish-based model of CNS remyelination can be added to the suite of current models to better understand the remyelination process and that some signalling mechanisms observed in mammals around myelination and OPC recruitment are likely conserved in the zebrafish. In addition, it could potentially be used to discover novel therapeutic targets that promote myelination in injury