Air Monitoring for Hazardous Gas Detection

The Hazardous Gas Detection Lab (HGDL) at Kennedy Space Center is involved in the design and development of instrumentation that can detect and quantify various hazardous gases. Traditionally these systems are designed for leak detection of the cryogenic gases used for the propulsion of the Shuttle and other vehicles. Mass spectrometers are the basis of these systems, which provide excellent quantitation, sensitivity, selectivity, response times and detection limits. A Table lists common gases monitored for aerospace applications. The first five gases, hydrogen, helium, nitrogen, oxygen, and argon are historically the focus of the HGDL

Clostridium perfringens α-toxin interaction with red cells and model membranes.

The effects of Clostridium perfringens α-toxin on host cells have previously been studied extensively but the biophysical processes associated with toxicity are poorly understood. The work reported here shows that the initial interaction between the toxin and lipid membrane leads to measurable changes in the physical properties and morphology of the membrane. A Langmuir monolayer technique was used to assess the response of different lipid species to toxin. Sphingomyelin and unsaturated phosphatidylcholine showed the highest susceptibility to toxin lypolitic action, with a two stage response to the toxin (an initial, rapid hydrolysis stage followed by the insertion and/or reorganisation of material in the monolayer). Fluorescence confocal microscopy on unsaturated phosphatidylcholine vesicles shows that the toxin initially aggregates at discrete sites followed by the formation of localised "droplets" accumulating the hydrolysis products. This process is accompanied by local increases in the membrane dipole potential by about 50 (±42) mV. In contrast, red blood cells incubated with the toxin suffered a decrease of the membrane dipole potential by 50 (±40) mV in areas of high toxin activity (equivalent to a change in electric field strength of 10(7) V m(-1)) which is sufficient to affect the functioning of the cell membrane. Changes in erythrocyte morphology caused by the toxin are presented, and the early stages of interaction between toxin and membrane are characterised using thermal shape fluctuation analysis of red cells which revealed two distinct regimes of membrane-toxin interaction.Royal Society University Research Fellowshi

Invaginating endoderm pulls on the extending ectoderm

How genetic programs generate cell-intrinsic forces to shape embryos is actively studied, but less so how tissue-scale physical forces impact morphogenesis. Here we address the role of the latter during axis extension, using Drosophila germband extension (GBE) as a model. We found previously that cells elongate in the anteroposterior (AP) axis in the extending germband, suggesting that an extrinsic tensile force contributed to body axis extension. Here we further characterized the AP cell elongation patterns during GBE, by tracking cells and quantifying their apical cell deformation over time. AP cell elongation forms a gradient culminating at the posterior of the embryo, consistent with an AP-oriented tensile force propagating from there. To identify the morphogenetic movements that could be the source of this extrinsic force, we mapped gastrulation movements temporally using light sheet microscopy to image whole Drosophila embryos. We found that both mesoderm and endoderm invaginations are synchronous with the onset of GBE. The AP cell elongation gradient remains when mesoderm invagination is blocked but is abolished in the absence of endoderm invagination. This suggested that endoderm invagination is the source of the tensile force. We next looked for evidence of this force in a simplified system without polarized cell intercalation, in acellular embryos. Using Particle Image Velocimetry, we identify posteriorwards Myosin II flows towards the presumptive posterior endoderm, which still undergoes apical constriction in acellular embryos as in wildtype. We probed this posterior region using laser ablation and showed that tension is increased in the AP orientation, compared to dorsoventral orientation or to either orientations more anteriorly in the embryo. We propose that apical constriction leading to endoderm invagination is the source of the extrinsic force contributing to germband extension. This highlights the importance of physical interactions between tissues during morphogenesis.This work was funded by a Biotechnology and Biological Sciences Research Council grant BB/ J010278/1 to GBB, RJA and BS, a Wellcome Trust Investigator Award 099234/Z/12/Z to BS and a Herchel Smith Postdoctoral Fellowship from the University of Cambridge to C

Derivation of Corneal Keratocyte-Like Cells from Human Induced Pluripotent Stem Cells

Corneal diseases such as keratoconus represent a relatively common disorder in the human population. However, treatment is restricted to corneal transplantation, which only occurs in the most advanced cases. Cell based therapies may offer an alternative approach given that the eye is amenable to such treatments and corneal diseases like keratoconus have been associated specifically with the death of corneal keratocytes. The ability to generate corneal keratocytes in vitro may enable a cell-based therapy to treat patients with keratoconus. Human induced pluripotent stem cells (hiPSCs) offer an abundant supply of cells from which any cell in the body can be derived. In the present study, hiPSCs were successfully differentiated into neural crest cells (NCCs), the embryonic precursor to keratocytes, and then cultured on cadaveric corneal tissue to promote keratocyte differentiation. The hiPSC-derived NCCs were found to migrate into the corneal stroma where they acquired a keratocyte-like morphology and an expression profile similar to corneal keratocytes in vivo. These results indicate that hiPSCs can be used to generate corneal keratocytes in vitro and lay the foundation for using these cells in cornea cell-based therapies

Normal levels of p27Xic1 are necessary for somite segmentation and determining pronephric organ size

The Xenopus laevis cyclin dependent kinase inhibitor p27Xic1 has been shown to be involved in exit from the cell cycle and differentiation of cells into a quiescent state in the nervous system, muscle tissue, heart and retina. We show that p27Xic1 is expressed in the developing kidney in the nephrostomal regions. Using over-expression and morpholino oligonucleotide (MO) knock-down approaches we show normal levels of p27Xic1 regulate pronephros organ size by regulating cell cycle exit. Knock-down of p27Xic1 expression using a MO prevented myogenesis, as previously reported; an effect that subsequently inhibits pronephrogenesis. Furthermore, we show that normal levels of p27Xic1 are required for somite segmentation also through its cell cycle control function. Finally, we provide evidence to suggest correct paraxial mesoderm segmentation is not necessary for pronephric induction in the intermediate mesoderm. These results indicate novel developmental roles for p27Xic1, and reveal its differentiation function is not universally utilised in all developing tissues

The influence of landscape composition and configuration on crop yield resilience

1. Sustainable agriculture aims to produce sufficient food while minimizing environmental damage. To achieve this, we need to understand the role of agricultural landscapes in providing diverse ecosystem services and how these affect crop production and resilience, that is, maintaining yields despite environmental perturbation. We used 10 years of English wheat yield data to derive three metrics of resilience (relative yield across the time series, yield stability around a moving average and resistance to an extreme weather event) at 10 km × 10 km resolution. We used remotely sensed maps to calculate measures of landscape structure, including composition (proportions of different land cover types) and configuration (metrics of connectivity and proximity), known to affect ecosystem service delivery (e.g. control of pests by beneficial invertebrates). We then used an information‐theoretic approach to identify the best‐fitting combination of landscape structure predictors for each resilience metric, using a potential yield model to account for the effects of climate and soils. Relative yield showed a strongly positive relationship with the area of arable land. For yield stability, this relationship was evident but alongside other landscape structure variables in the best‐fitting model. No relationship with arable land was evident for resistance. Yield stability showed a strongly positive effect of proximity to semi‐natural habitats. For resistance, the best‐fitting model included positive relationships with the cover of semi‐natural habitats and proximity to semi‐natural grasslands. Synthesis and applications. Landscapes with the highest relative wheat yields did not show the highest yield stability or resistance to extreme events. As resilience metrics were derived from shorter portions of the time series, the importance of semi‐natural habitats compared to arable land increased. This is probably driven by the complex interplay between landscape structure, agricultural management and ecosystem services. These results demonstrate that measuring relative yield over time may be insufficient to capture the full effect that non‐arable components of the landscape, and the ecosystem services they deliver, have on other aspects of resilience, and that there are clear trade‐offs in managing agricultural landscapes to maximize different aspects of crop yield resilience

Clostridium perfringens epsilon toxin mutant Y30A-Y196A as a recombinant vaccine candidate against enterotoxemia

Epsilon toxin (Etx) is a β-pore-forming toxin produced by Clostridium perfringens toxinotypes B and D and plays a key role in the pathogenesis of enterotoxemia, a severe, often fatal disease of ruminants that causes significant economic losses to the farming industry worldwide. This study aimed to determine the potential of a site-directed mutant of Etx (Y30A-Y196A) to be exploited as a recombinant vaccine against enterotoxemia. Replacement of Y30 and Y196 with alanine generated a stable variant of Etx with significantly reduced cell binding and cytotoxic activities in MDCK.2 cells relative to wild type toxin (>430-fold increase in CT50) and Y30A-Y196A was inactive in mice after intraperitoneal administration of trypsin activated toxin at 1000× the expected LD50 dose of trypsin activated wild type toxin. Moreover, polyclonal antibody raised in rabbits against Y30A-Y196A provided protection against wild type toxin in an in vitro neutralisation assay. These data suggest that Y30A-Y196A mutant could form the basis of an improved recombinant vaccine against enterotoxemia

Reversibilidade de bens na concessão do serviço telefônico fixo comutado : uma análise crítica na perspectiva da Teoria Responsiva da Regulação

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Direito, Curso de Pós-Graduação em Direito, 2017.A presente dissertação investiga as possíveis consequências de mutações paradigmáticas do direito administrativo no contorno jurídico de um instituto considerado, tradicionalmente, intrínseco às concessões de serviço de telecomunicações: a reversão de bens. O estudo evidencia a relação das alterações doutrinárias dos institutos jurídicos do direito administrativo com a persistência dos bens reversíveis nas concessões de serviços de telecomunicações. Destarte, a linha investigativa do trabalho identifica se o instituto da reversibilidade de bens na concessão de serviço público de telecomunicações é, ainda, a única ou melhor forma de se atingir os fins por ele visados, em especial a continuidade do serviço. Em relação ao marco teórico, adotou-se a teoria responsiva da regulação, tal como concebida por Ian Ayres e John Braithwaite no livro Responsive Regulation: Transcending the Deregulation Debate, de 1992, e desdobramentos de pesquisas posteriores. A pesquisa inicia com investigação sobre o novo papel a ser desempenhado pela Administração Pública em sua atuação em geral e, especificamente, no âmbito regulatório. Em seguida, propõe-se a adoção da teoria responsiva da regulação como modelagem teórica adequada para conciliar uma nova forma de atuação administrativa com a proteção dos interesses públicos. Após um aprofundamento sobre as principais proposições da teoria responsiva, foram analisados a doutrina e o arcabouço normativo sobre o tema dos bens reversíveis no setor de telecomunicações, propondo-se, ao final, uma crítica à regulamentação atual e fornecendo-se uma possível modelagem que seguisse os ditames da teoria responsiva da regulação.This study investigates the possible consequences of paradigmatic changes in Administrative Law in the legal context of an institute considered, at least traditionally, intrinsic to telecommunications service in Brazil: the reversal to the public domain or to a new service provider of assets owned by the current service provider. It is intended to highlight the relationship between the doctrinal changes in the legal institutes of Administrative Law and the persistence of the reversible assets in telecommunications service. Thus, the investigative line of the work will seek to know if the institute of the reversibility of asset in public telecommunications services is still the only or the better way to achieve its goals, especially the continuity of the service, from the perspective of the theory of responsive regulation, as conceived by Ian Ayres and John Braithwaite in the book Responsive Regulation: Transcending the Deregulation Debate, 1992. The research begins with developments on the new role to be played by the Public Administration, not least in the regulatory arena. Next, the study tackles the appropriateness of the theory of responsive regulation to reconcile a new form of administrative action with the protection of public interests. After that the main propositions of the theory of responsive regulation, the doctrine and the normative framework on the subject of reversible assets in the telecommunications sector were analyzed. Finally, a critique of current state of the art of the regulation and proposals providing a possible modeling that follows the dictates of the Responsive Theory of Regulation were made

Molecular architecture and functional analysis of NetB, a pore-forming toxin from Clostridium perfringens

NetB is a pore-forming toxin produced by Clostridium perfringens and has been reported to play a major role in the pathogenesis of avian necrotic enteritis, a disease that has emerged due to the removal of antibiotics in animal feedstuffs. Here we present the crystal structure of the pore-form of NetB solved to 3.9Å. The heptameric assembly shares structural homology to the Staphylococcal α-hemolysin. However, the rim domain, a region that is thought to interact with the target cell membrane shows sequence and structural divergence leading to the alteration of a phosphocholine binding pocket found in the staphylococcal toxins. Consistent with the structure we show that NetB does not bind phosphocholine efficiently but instead interacts directly with cholesterol leading to enhanced oligomerisation and pore formation. Finally we have identified conserved and non-conserved amino acid positions within the rim loops that significantly affect binding and toxicity of NetB. These findings present new insights into the mode of action of these pore-forming toxins enabling the design of more effective control measures against necrotic enteritis and providing potential new tools to the field of bionanotechnology