1,670 research outputs found
Die Demethylierung von Dimethylselenid ist eine adaptive Antwort des Archaeons Methanococcus voltae
Im natĂŒrlichen Lebensraum von Methanococcus voltae
kommt Selen in unterschiedlichen Verbindungen und Konzentration
vor. So variiert der Selengehalt im MĂŒndungswasser
verschiedener FlĂŒsse zwischen 0,1 und 63 nM. Aufgrund der guten
Löslichkeit sind die Oxianionen des Selens biologisch am
interessantesten. Sie sind daher aber auch in hohen
Konzentrationen toxisch. Selen in geringen Mengen ist dagegen
essentiell, da es als Selenomethionin oder -cystein in
Proteinen vorkommen kann. Eine hÀufig anzutreffende organische
Selenverbindungen ist das Dimethylselenid (DMSe). Diese
flĂŒchtige Substanz wird von einer Vielzahl Organismen zur
Detoxifizierung gebildet. Aus M. voltae sind insgesamt 4
Hydrogenasen bekannt, wovon zwei ein Selenocystein aufweisen
und konstitutiv exprimiert werden. Die Induktion der
Transkription der selenfreien Isoenzyme erfolgt dagegen bei
Selenmangel. In Expressionsanalysen zeigte sich, dass 5 weitere
Proteine ebenfalls nur unter Selenlimitierung synthetisiert
werden. Von zweien wurde jeweils die N-terminale Peptidsequenz
und von einem zusÀtzlich interne Peptidsequenzen bestimmt. In
der vorliegenden Arbeit wurde zunÀchst das Gen eines dieser
Proteine identifiziert. In einer Datenbanksuche stellte sich
dann heraus, dass es SequenzidentitÀten mit Corrinoid-Proteinen
aus Methanosarcina aufwies. Es wurde als SdmA bezeichnet (fĂŒr
Dimethylselenid Demethylierung). Das Gen sdmA liegt zusammen
mit sdmB und sdmC auf einem gemeinsamen polycistronischen
Messenger, der nur bei Selenmangel nachweisbar war. SdmB und
SdmC haben gemeinsame Sequenzmotive mit Methyltransferasen, die
in einigen Methanoarchaeen an der methylotrophen Methanogenese
beteiligt sind. Dabei ĂŒbertragen diese die Methylgruppe von
Corrinoid-Proteinen auf den Akzeptor Coenzym M. Die
Methylgruppe stammt dabei beispielsweise aus methylierten
Aminen bzw. Thiolen oder aus Methanol. Normalerweise werden von
M. voltae fĂŒr die Methanogenese nur Formiat oder H2/CO2
erschlossen, so bestÀtigte sich die Vermutung nicht, dass bei
Selenmangel SdmA, SdmB und SdmC die ErschlieĂung der oben
genannten methylierten Substrate erlauben könnten. Versetzt man
das Selenmangelmedium jedoch mit DMSe, dann fĂŒhrt dies zur
Repression des Promotors der Gene einer selenfreien
Hydrogenase, der normalerweise nur unter Selenlimitierung aktiv
wĂ€re. Eine Deletion von sdmA oder sdmC fĂŒhrte zur AktivitĂ€t des
Promotors trotz der Anwesenheit von DMSe. Der Austausch von
sdmB hatte dagegen keinen Effekt. Zudem waren die
Wachstumsraten der Mutanten delta sdmA und delta sdmB im
Vergleich zum Wildtyp trotz DMSe-Zugabe reduziert. In M. voltae
scheint es daher zwei verschiedene Anpassungsmechanismen an
Selenmangel zu geben. Zum einen werden unter Selenlimitierung
die selenfreien Isoenzyme der selenhaltigen Hydrogenasen
exprimiert und zum anderen lÀsst sich unter diesen Bedingungen
ein alternatives Selensubstrat, wie das DMSe, von M. voltae zur
Biosynthese der Selenoproteine erschlieĂen. Daran ist
vermutlich das Corrinoid-Proteine SdmA und die
Methyltransferase SdmC beteiligt
Vicious or Virtuous Cycle? The Privacy Implications of Active Assisted Living Technologies for Older People
A variety of technologies are being developed to help older people live healthier, more independent, and safer lives, for longer. While many of these technologies are positively impacting the lives of older adults, they also have the potential to dictate specific behaviours or restrict their autonomy rather than empower them. The vulnerability theory of privacy proposes that vulnerable populations are not only more likely to be susceptible to privacy violations, but are also disproportionately affected by said violations. In this position paper, we adapt the vulnerability theory of privacy to the older adult population, and identify a further potential exacerbatory cycle. The risk of a 'slippery slope' of privacy violation occurs when AAL technologies enable an elevated and quantified visibility of (mis)behaviour and irregular activity that could seem to justify the deployment of further AAL technology. We present ÄâŹ?FOR VERIFICATION>ratchet-wise rehabilitation' as an alternative vision to the ÄâŹ?FOR VERIFICATION>slippery slope' and identify research and design challenges throughout the paper
Predictions of selected flavour observables within the Standard Model
This letter gathers a selection of Standard Model predictions issued from the
metrology of the CKM parameters performed by the CKMfitter group. The selection
includes purely leptonic decays of neutral and charged B, D and K mesons. In
the light of the expected measurements from the LHCb experiment, a special
attention is given to the radiative decay modes of B mesons as well as to the
B-meson mixing observables, in particular the semileptonic charge asymmetries
a^d,s_SL which have been recently investigated by the D0 experiment at
Tevatron. Constraints arising from rare kaon decays are addressed, in light of
both current results and expected performances of future rare kaon experiments.
All results have been obtained with the CKMfitter analysis package, featuring
the frequentist statistical approach and using Rfit to handle theoretical
uncertainties.Comment: 8 pages, 1 figure, 2 tables. Typos corrected and discussion of
agreement between SM and data update
Study of the acoustic signature of UHE neutrino interactions in water and ice
The production of acoustic signals from the interactions of ultra-high energy
(UHE) cosmic ray neutrinos in water and ice has been studied. A new
computationally fast and efficient method of deriving the signal is presented.
This method allows the implementation of up to date parameterisations of
acoustic attenuation in sea water and ice that now includes the effects of
complex attenuation, where appropriate. The methods presented here have been
used to compute and study the properties of the acoustic signals which would be
expected from such interactions. A matrix method of parameterising the signals,
which includes the expected fluctuations, is also presented. These methods are
used to generate the expected signals that would be detected in acoustic UHE
neutrino telescopes.Comment: 21 pages and 13 figure
Studies on muon tomography for archaeological internal structures scanning
International audienceMuon tomography is a potential non-invasive technique for internal structure scanning. It has already interesting applications in geophysics and can be used for archaeological purposes. Muon tomography is based on the measurement of the muon flux after crossing the structure studied. Differences on the mean density of these structures imply differences on the detected muon rate for a given direction. Based on this principle, Monte Carlo simulations represent a useful tool to provide a model of the expected muon rate and angular distribution depending on the composition of the studied object, being useful to estimate the expected detected muons and to better understand the experimental results. These simulations are mainly dependent on the geometry and composition of the studied object and on the modelling of the initial muon flux at surface. In this work, the potential of muon tomography in archaeology is presented and evaluated with Monte Carlo simulations by estimating the differences on the muon rate due to the presence of internal structures and its composition. The influence of the chosen muon model at surface in terms of energy and angular distributions in the final result has been also studied. 1. Introduction Among the different applications that muon tomography can have, the scanning of archaeological structures is one of the most innovative one. The principle of the method is straightforward. By detecting the muons that cross the studied object and reconstructing their directions, it is possible to identify the existence of significant differences in the muon rate for a given direction. These differences, consequence of a variation of the mean density of the object traversed by the muons, indicate the possible existence of an internal structure inside the object. The reconstruction of these internal structures by the analysis of the directions of the registered muons is frequently called inverse method. Some features of muon tomography are specially interesting for archaeology. It is a passive method since it is based on the detection of the atmospheric muons, which are naturally produced. Moreover, it is a non-invasive technique since the detector would be placed outside the object to study or, if possible, inside it if internal corridors and halls already exist, as i
Gapeau: Enhancing the Sense of Distance to Others with a Head-Mounted Sensor
Human perception lacks the capabilities to accurately assess distance. The recent Covid-19 pandemic outbreak rendered this ability particularly important. Augmenting our sense of distance can help maintain safe separation from others when required. To explore how systems can help users maintain physical distance, we designed, implemented and evaluated Gapeau - a head-mounted system for augmenting the sense of distance. Our system uses proximity sensors and thermal sensing to detect and measure the distance to other people. We conducted a validation protocol, an experiment, in which we compared different feedback modalities, and an in-the-wild study to evaluate Gapeau\u27s performance and suitability for use in social contexts. We found that our system enabled users to more accurately determine whether they were maintaining a safe distance from others. Vibration and auditory feedback were found most effective and usable. Gapeau was perceived as socially acceptable. Our work contributes insights for augmented sensing systems with social relevance
CX3CR1 Polymorphisms are associated with atopy but not asthma in German children
Chemokines and their receptors are involved in many aspects of immunity. Chemokine CX3CL1, acting via its receptor CX3CR1, regulates monocyte migration and macrophage differentiation as well as T cell-dependent inflammation. Two common, nonsynonymous polymorphisms in CX3CR1 have previously been shown to alter the function of the CX3CL1/CX3CR1 pathway and were suggested to modify the risk for asthma. Using matrix-assisted laser desorption/ionization time-of-flight technology, we genotyped polymorphisms Val249Ile and Thr280Met in a cross-sectional population of German children from Munich (n = 1,159) and Dresden ( n = 1,940). For 249Ile an odds ratio of 0.77 (95% confidence interval 0.63-0.96; p = 0.017) and for 280Met an odds ratio of 0.71 ( 95% confidence interval 0.56-0.89; p = 0.004) were found with atopy in Dresden but not in Munich. Neither polymorphism was associated with asthma. Thus, amino acid changes in CX3CR1 may influence the development of atopy but not asthma in German children. Potentially, other factors such as environmental effects may modify the role of CX3CR1 polymorphisms. Copyright (c) 2007 S. Karger AG, Basel
Migrating Songbirds on Stopover Prepare for, and Recover from, Oxidative Challenges Posed by Long-Distance Flight
Managing oxidative stress is an important physiological function for all aerobic organisms, particularly during periods of prolonged high metabolic activity, such as long-distance migration across ecological barriers. However, no previous study has investigated the oxidative status of birds at different stages of migration and whether that oxidative status depends on the condition of the birds. In this study, we compared (1) energy stores and circulating oxidative status measures in (a) two species of Neotropical migrants with differing migration strategies that were sampled at an autumn stopover site before an ecological barrier; and (b) a species of trans-Saharan migrant sampled at a spring stopover site after crossing an ecological barrier; and (2) circulating oxidative measures and indicators of fat metabolism in a trans-Saharan migrant after stopovers of varying duration (0â8 nights), based on recapture records. We found fat stores to be positively correlated with circulating antioxidant capacity in Blackpoll Warblers and Red-eyed Vireos preparing for fall migration on Block Island, USA, but uncorrelated in Garden Warblers on the island of Ponza, Italy, after a spring crossing of the Sahara Desert and Mediterranean Sea. In all circumstances, fat stores were positively correlated with circulating lipid oxidation levels. Among Garden Warblers on the island of Ponza, fat anabolism increased with stopover duration while oxidative damage levels decreased. Our study provides evidence that birds build antioxidant capacity as they build fat stores at stopover sites before long flights, but does not support the idea that antioxidant stores remain elevated in birds with high fuel levels after an ecological barrier. Our results further suggest that lipid oxidation may be an inescapable hazard of using fats as the primary fuel for flight. Yet, we also show that birds on stopover are capable of recovering from the oxidative damage they have accrued during migration, as lipid oxidation levels decrease with time on stopover. Thus, the physiological strategy of migrating songbirds may be to build prophylactic antioxidant capacity in concert with fuel stores at stopover sites before a long-distance flight, and then repair oxidative damage while refueling at stopover sites after long-distance flight
Frequent use of paracetamol and risk of allergic disease among women in an Ethiopian population
Introduction
The hypothesis that paracetamol might increase the risk of asthma and other allergic diseases have gained support from a range of independent studies. However, in studies based in developed countries, the possibility that paracetamol and asthma are associated through aspirin avoidance is difficult to exclude.
Objectives
To explore this hypothesis among women in a developing country, where we have previously reported aspirin avoidance to be rare.
Methods
In 2005/6 a population based cohort of 1065 pregnant women was established in Butajira, Ethiopia and baseline demographic data collected. At 3 years post birth, an interview-based questionnaire administered to 945 (94%) of these women collected data on asthma, eczema, and hay fever in the past 12 month, frequency of paracetamol use and potential confounders. Allergen skin tests to Dermatophagoides pteronyssinus and cockroach were also performed. The independent effects of paracetamol use on allergic outcomes were determined using multiple logistic regression analysis.
Findings
The prevalence of asthma, eczema and hay fever was 1.7%, 0.9% and 3.8% respectively; of any one of these conditions 5.5%, and of allergen sensitization 7.8%. Paracetamol use in the past month was reported by 29%, and associations of borderline significance were seen for eczema (adjusted OR (95% CI) = 8.51 (1.68 to 43.19) for 1â3 tablets and 2.19 (0.36 to 13.38) for â„4 tablets, compared to no tablets in the past month; overall p = 0.055) and for âany allergic conditionâ (adjusted OR (95% CI) = 2.73 (1.22 to 6.11) for 1â3 tablets and 1.35 (0.67 to 2.70) for â„4 tablets compared to 0 in the past month; overall p = 0.071).
Conclusions
This study provides further cross-sectional evidence that paracetamol use increases the risk of allergic disease
LOOP:Exploring Physicalization of Activity Tracking Data
Wearables, mobile devices and Internet-of-Things (IoT) sensors are enabling us to monitor our environment, understand our social connections, and track our personal health. However, most of these systems communicate data through information visualizations that are often âhiddenâ inside devices, such as mobile phones and tablets, requiring users to undertake explicit actions to reveal them. Novel interfaces and devices embedded in peopleâs everyday life have the potential to help users visualize, use, and appropriate their collected personal data. To this end, we designed the physical artifact LOOP, which provides an abstract visualization of the userâs activity data by changing its shape. In this paper, we elaborate on the design and present a one-week field study in which LOOP was deployed in the homes of five end-users. We found that the physical presence of LOOP facilitated reflection and the layered visualization supported various personal tracking
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