Development of a high-throughput shotgun-mass spectrometry method for qualitative and quantitative analysis of major mammalian brain gangliosides

The goal of this thesis was to develop a high-throughput shotgun-MS lipidomics method to qualitatively and quantitively analyze the major mammalian brain ganglioside classes: GM1, GD1, GT1 and GQ1. As a starting point for the method to be developed, a modified ganglioside extraction method from Svennerholm and Ladisch was used (Svennerholm and Fredman, 1980; Ladisch and Gillard, 1985). The efficiencies and the impact of different extraction procedures to the overall performance were evaluated with a software called OptiVal™. The evaluation showed that the most important steps of the protocol are the salt concentration of the water phase during the 2-phase extraction, and 10 mM NaCl yielded the best sensitivity. Also, the number of washing steps with water during reverse solid phase extraction using C18 resin has a significant effect. The next step was to find suitable standards for quantification of the individual ganglioside classes. Since deuterated and alike ganglioside standards were commercially not available, we initially used a deuterated PE standard with limited success. A collaboration with the Ludger Johannes lab provided us with modified C17-ganglioside standards. The term “modified” describes the enzymatic exchange of the fatty acid in the hydrophobic tail by a 17-carbon atom long fatty acid. Since odd numbered fatty acids occur very rarely in nature, it is possible to use the measured intensity of the modified ceramide headgroup of 35:1 (Sphingosine C18:1 + Fatty Acid C17:0) to quantify natural gangliosides. Ideally, we would need to have a fitting modified C17-ganglioside standard for each class to be quantified. Since first only GM1 as a modified standard was available, it was necessary to determine response factors (RFs) for the ganglioside classes GD1, GT1 and GQ1. RFs were assessed empirically by titrating a variety of equimolar concentrations of the modified C17-GM1 standard versus wildtype standards of the other ganglioside classes. After establishment of the RFs it was possible to determine the limits of detection (LOD) and quantification (LOQ) for the ganglioside classes GD1, GT1 and GQ1 - with regard to the modified C17-GM1 standard. When the modified C17-standards for GD1 and GT1 became available, I was able to find out whether the correct internal standards are superior to the proxy method via response factors. The results clearly showed that the use of a correct class standards is preferable. For GQ1 no modified C17-standard was obtainable, therefore this class still has to be quantified via RFs. Experiments showed that the modified C17-GT1 standard is best suited for that. Another major goal was to integrate the ganglioside method into the general lipid analysis workflow of the high-throughput shotgun mass spectrometry platform that we were using. To achieve these goals adjustments on the evaluated (=old) protocol had to be done. These adjustments included changes in the extraction steps from the Svennerholm & Ladisch more into the direction of a Bligh & Dyer based extraction method. This meant abandoning the 2-phase extraction step as well as the chloroform/methanol/water (C/M/W) 4:8:3 extraction, in favor of a C/M 10:1 followed by a C/M 2:1 extraction of 150 mM ammonium-bicarbonate water solution. The goal behind this was to enable a combination of the global lipidome extraction (Surma et al., 2015) with the ganglioside extraction. Another important improvement was scaling up the extraction process. The use of standard single solid phase extraction (SPE) cartridges was limiting the extraction throughput to only 24 samples at a time, therefore the single SPE cartridges were replaced with the 96-well SPE SOLA™ plates. To process the SOLA™ plates it was necessary to establish the usage of a vacuum manifold. Combined, these changes lowered the overall process time of the protocol from nearly two working days to one working day, without significant loss of sensitivity regarding the measured sample concentrations. This was assessed by performing the mouse brain tissue titration experiment, with all three modified C17-ganglioside class standards GM1, GD1 and GT1. Finally, the established method was applied to investigate the difference in ganglioside levels in the cerebellum compared to the brain hemispheres in mice of different age. First the C/M 10:1 and 2:1 extraction was done for the analysis of all non-ganglioside lipids in the sample. The leftover water phase was then loaded onto the SOLA™ plates and processed with the new protocol. The results matched the given goals - to establish a protocol to measure and quantify the four major brain ganglioside classes in combination with the global lipidomics in a high-throughput manner - and thus were a success. To the best of our knowledge, this was the first time such a broad lipidomic measurement has been performed, hence no other studies exist to which the outcome could be compared

On the optimality of the uniform random strategy

The concept of biased Maker-Breaker games, introduced by Chv\'atal and Erd{\H o}s, is a central topic in the field of positional games, with deep connections to the theory of random structures. For any given hypergraph ${\cal H}$ the main questions is to determine the smallest bias $q({\cal H})$ that allows Breaker to force that Maker ends up with an independent set of ${\cal H}$. Here we prove matching general winning criteria for Maker and Breaker when the game hypergraph satisfies a couple of natural `container-type' regularity conditions about the degree of subsets of its vertices. This will enable us to derive a hypergraph generalization of the $H$-building games, studied for graphs by Bednarska and {\L}uczak. Furthermore, we investigate the biased version of generalizations of the van der Waerden games introduced by Beck. We refer to these generalizations as Rado games and determine their threshold bias up to constant factors by applying our general criteria. We find it quite remarkable that a purely game theoretic deterministic approach provides the right order of magnitude for such a wide variety of hypergraphs, when the generalizations to hypergraphs in the analogous setup of sparse random discrete structures are usually quite challenging.Comment: 26 page

Bond currency denomination and the yen carry trade

We examine the determinants of issuance of yen-denominated international bonds over the period from 1990 through 2010. This period was marked by low Japanese interest rates that led some investors to pursue "carry trades," which consisted of funding investments in higher interest rate currencies with low interest rate, yen-denominated obligations. In principle, bond issuers that have flexibility in their funding currency could also conduct a carry-trade strategy by funding in yen during this low interest rate period. We examine the characteristics of firms who appeared to have adopted this strategy using a data set containing almost 80,000 international bond issues. Our results suggest that there was a movement towards issuing in yen in the international bond markets starting in 2003, but this appears to have ended with the outbreak of the global financial crisis in 2007. Furthermore, the breakdown of carry-trade conditions in 2007 corresponds to a resurgence in the ability of economic fundamentals, such as the volume of trade with Japan, to explain the decision to issue international bonds denominated in yen.Bond market ; Yen, Japanese

Humusmanagement und Humusbilanz hessischer Öko-Betriebe

Mit dem Projekt „Humusmanagement und Humusbilanz hessischer Öko-Betriebe“ soll das Verständnis von Möglichkeiten und Grenzen des Humusmanagements unter Bedingungen des ökologischen Landbaus gefördert werden. Gleichzeitig bietet das Projekt Einblicke in die Humusbilanzierung und die daraus zu ziehenden Analysen und Bewertungen. Zielgruppen sind dabei gleichermaßen Praktiker, Berater und Wissenschaftler. Selbst in wissenschaftlichen Fachgruppen herrscht derzeit keine Einigung über die geeignete Methodik zur Humusbilanzierung und deren letztendliche Aussagekraft. Diese Broschüre bietet Praktikern und Beratern deshalb einen Überblick über die Methodik und damit eine Handreichung für die wichtigsten Fragen zur Humusbilanz und -versorgung: Wie berechne und interpretiere ich eine Humusbilanz richtig? Wie ist die reale Situation der Humusversorgung im Ökolandbau? Wie kann ich meine Humusbilanz verbessern? Für die Wissenschaftler stehen die folgenden Fragen im Vordergrund: Wie managen Praxisbetriebe die Humusversorgung ihrer Ackerböden? Wie steht es um die Anwendbarkeit von Humusbilanzmethoden in der Praxis des ökologischen Acker-, Gemüse- und Gartenbaus und wo besteht welcher Forschungs- und/oder Entwicklungsbedarf

The Social Psychology Of Perception Experiments: Hills, Backpacks, Glucose, And The Problem Of Generalizability

Experiments take place in a physical environment but also a social environment. Generalizability from experimental manipulations to more typical contexts may be limited by violations of ecological validity with respect to either the physical or the social environment. A replication and extension of a recent study (a blood glucose manipulation) was conducted to investigate the effects of experimental demand (a social artifact) on participant behaviors judging the geographical slant of a large-scale outdoor hill. Three different assessments of experimental demand indicate that even when the physical environment is naturalistic, and the goal of the main experimental manipulation was primarily concealed, artificial aspects of the social environment (such as an explicit requirement to wear a heavy backpack while estimating the slant of a hill) may still be primarily responsible for altered judgments of hill orientation. (PsycINFO Database Record (c) 2013 APA, all rights reserved)(journal abstract

The burden of malaria in post-emergency refugee sites: A retrospective study

<p>Abstract</p> <p>Background</p> <p>Almost two-thirds of refugees, internally displaced persons, returnees and other persons affected by humanitarian emergencies live in malaria endemic regions. Malaria remains a significant threat to the health of these populations.</p> <p>Methods</p> <p>Data on malaria incidence and mortality were analyzed from January 2006 to December 2009 from the United Nations High Commissioner for Refugees Health Information System database collected at sites in Burundi, Chad, Cameroon, Ethiopia, Kenya, Sudan, Tanzania, Thailand, and Uganda. Data from three countries during 2006 and 2007, and all nine countries from 2008 to 2009, were used to describe trends in malaria incidence and mortality. Monthly counts of malaria morbidity and mortality were aggregated into an annual country rate averaged over the study period.</p> <p>Results</p> <p>An average of 1.18 million refugees resided in 60 refugee sites within nine countries with at least 50 cases of malaria per 1000 refugees during the study period 2008-2009. The highest incidence of malaria was in refugee sites in Tanzania, where the annual incidence of malaria was 399 confirmed cases per 1,000 refugees and 728 confirmed cases per 1,000 refugee children younger than five years. Malaria incidence in children younger than five years of age, based on the sum of confirmed and suspected cases, declined substantially at sites in two countries between 2006 and 2009, but a slight increase was reported at sites within four of seven countries between 2008 and 2009. Annual malaria mortality rates were highest in sites in Sudan (0.9 deaths per 1,000 refugees), Uganda and Tanzania (0.7 deaths per 1000 refugees each). Malaria was the cause of 16% of deaths in refugee children younger than five years of age in all study sites.</p> <p>Conclusions</p> <p>These findings represent one of the most extensive reports on malaria among refugees in post-emergency sites. Despite declines in malaria incidence among refugees in several countries, malaria remains a significant cause of mortality among children younger than five years of age. Further progress in malaria control, both within and outside of post-emergency sites, is necessary to further reduce malaria incidence and mortality among refugees and achieve global goals in malaria control and elimination.</p

Prevalence of Gastroesophageal Reflux Disease and Proton Pump Inhibitor-Refractory Symptoms

Background &amp; aimsThere are few data on the prevalence of gastroesophageal reflux disease (GERD) in the United States. We performed a population-based study to determine the prevalence of GERD symptoms and persistent GERD symptoms despite use of proton pump inhibitors (PPIs).MethodsWe conducted the National Gastrointestinal Survey in 2015 using MyGiHealth, an app that guides participants through National Institutes of Health gastrointestinal Patient-Reported Outcomes Measurement Information System surveys. Primary outcomes were prevalence of GERD symptoms in the past and persistence of GERD symptoms (heartburn or regurgitation 2 or more days in past week) among participants taking PPIs. Population weights were applied to the data and multivariable regression was used to adjust for confounding.ResultsAmong 71,812 participants, 32,878 (44.1%) reported having had GERD symptoms in the past and 23,039 (30.9%) reported having GERD symptoms in the past week. We also found that 35.1% of those who had experienced GERD symptoms were currently on therapy (55.2% on PPIs, 24.3% on histamine-2 receptor blockers, and 24.4% on antacids). Among 3229 participants taking daily PPIs, 54.1% had persistent GERD symptoms. Younger individuals, women, Latino individuals, and participants with irritable bowel syndrome or Crohn's disease were more likely to have continued symptoms, even when taking PPIs.ConclusionsUsing a population-based survey, we found GERD symptoms to be common: 2 of 5 participants have had GERD symptoms in the past and 1 of 3 had symptoms in the past week. We also found that half of PPI users have persistent symptoms. Given the significant effect of GERD on quality of life, further research and development of new therapies are needed for patients with PPI-refractory GERD symptoms

Incidence and risk factors for Malaria, pneumonia and diarrhea in children under 5 in UNHCR refugee camps: A retrospective study

<p>Abstract</p> <p>Background</p> <p>United Nations High Commissioner for Refugees (UNHCR) refugee camps are located predominantly in rural areas of Africa and Asia in protracted or post-emergency contexts. Recognizing the importance of malaria, pneumonia and diarrheal diseases as major causes of child morbidity and mortality in refugee camps, we analyzed data from the UNHCR Health Information System (HIS) to estimate incidence and risk factors for these diseases in refugee children younger than five years of age.</p> <p>Methods</p> <p>Data from 90 UNHCR camps in 16 countries, including morbidity, mortality, health services and refugee health status, were obtained from the UNHCR HIS for the period January 2006 to February 2010. Monthly camp-level data were aggregated to yearly estimates for analysis and stratified by location in Africa (including Yemen) or Asia. Poisson regression models with random effects were constructed to identify factors associated with malaria, pneumonia and diarrheal diseases. Spatial patterns in the incidence of malaria, pneumonia and diarrheal diseases were mapped to identify regional heterogeneities.</p> <p>Results</p> <p>Malaria and pneumonia were the two most common causes of mortality, with confirmed malaria and pneumonia each accounting for 20% of child deaths. Suspected and confirmed malaria accounted for 23% of child morbidity and pneumonia accounted for 17% of child morbidity. Diarrheal diseases were the cause of 7% of deaths and 10% of morbidity in children under five. Mean under-five incidence rates across all refugee camps by region were: malaria [Africa 84.7 cases/1000 U5 population/month (95% CI 67.5-102.0), Asia 2.2/1000/month (95% CI 1.4-3.0)]; pneumonia [Africa 59.2/1000/month (95% CI 49.8-68.7), Asia 254.5/1000/month (95% CI 207.1-301.8)]; and diarrheal disease [Africa 35.5/1000/month (95% CI 28.7-42.4), Asia 69.2/1000/month (95% CI 61.0-77.5)]. Measles was infrequent and accounted for a small proportion of child morbidity (503 cases, < 1%) and mortality (6 deaths, < 1%).</p> <p>Conclusions</p> <p>As in stable settings, pneumonia and diarrhea are important causes of mortality among refugee children. Malaria remains a significant cause of child mortality in refugee camps in Africa and will need to be addressed as part of regional malaria control and elimination efforts. Little is known of neonatal morbidity and mortality in refugee settings, and neonatal deaths are likely to be under-reported. Global measles control efforts have reduced the incidence of measles among refugee children.</p

4D Printing at the Microscale

3D printing of adaptive and dynamic structures, also known as 4D printing, is one of the key challenges in contemporary materials science. The additional dimension refers to the ability of 3D printed structures to change their properties—for example, shape—over time in a controlled fashion as the result of external stimulation. Within the last years, significant efforts have been undertaken in the development of new responsive materials for printing at the macroscale. However, 4D printing at the microscale is still in its early stages. Thus, this progress report will focus on emerging materials for 4D printing at the microscale as well as their challenges and potential applications. Hydrogels and liquid crystalline and composite materials have been identified as the main classes of materials representing the state of the art of the growing field. For each type of material, the challenges and critical barriers in the material design and their performance in 4D microprinting are discussed. Importantly, further necessary strategies are proposed to overcome the limitations of the current approaches and move toward their application in fields such as biomedicine, microrobotics, or optics

Towards a unified model of stellar rotation II: Model-dependent characteristics of stellar populations

Rotation has a number of important effects on the evolution of stars. Apart from structural changes because of the centrifugal force, turbulent mixing and meridional circulation caused by rotation can dramatically affect a star's chemical evolution. This leads to changes in the surface temperature and luminosity as well as modifying its lifetime. Observationally rotation decreases the surface gravity, causes enhanced mass loss and leads to surface abundance anomalies of various chemical isotopes. The replication of these physical effects with simple stellar evolution models is very difficult and has resulted in the use of numerous different formulations to describe the physics. Using stellar evolution calculations based on several physical models we discuss the features of the resulting simulated stellar populations which can help to distinguish between the models.Comment: 14 pages, 13 figures. Accepted for publication in MNRA