An analysis of the role of glutathione and p53 in the response to oxidative injury

The response to oxidative stress, a process that can lead to genotoxic injury, is thought to involve the abundant cellular antioxidant, glutathione, and the stress response transcription factor, p53. Glutathione (GSH) biosynthesis occurs through a two -step pathway, the first reaction of which is rate limiting and is catalysed by the enzyme gamma glutamylcysteine synthetase (yGCS). yGCS is a heterodimer, composed of a heavy (yGCSh) and a light ( yGCS1) subunit. The heavy subunit contains the active site, whereas the light performs a regulatory function on the heavy by means of a redox -sensitive inter- subunit disulphide bridge.The hypothesis that GSH mediates protection against oxidative stress was investigated by gene targeting of yGCSh in murine embryonic stem (ES) cells. Mouse yGCSh cDNA sequence was isolated by RT -PCR, cloned, characterised and used to screen a mouse genomic ? library. Characterisation of the resultant clone confirmed that it contained yGCSh gene sequences. This information was used to design and construct a replacement targeting vector which was subsequently electroporated into ES cells to delete a segment of the endogenous locus. A total of 285 clones were isolated and analysed for a correct gene targeting event. Unfortunately, no positive clones were identified.The role of GSH and p53 in the response of ES cells to oxidative stress was also examined via a series of in vitro assay strategies measuring cellular viability, apoptosis and intracellular GSH levels. ES cells were shown to express yGCSh. Agents known to induce oxidative stress or lower GSH levels in other cell lines were then tested for toxicity and their potential to modulate GSH levels in ES cells. On the basis of these experiments, the quinone menadione (MQ) and the yGCS inhibitor, buthionine sulphoximine (BSO), were investigated further. Treatment with MQ was associated with a transient elevation of GSH, a strong apoptotic response and reduced clonogenic survival. Addition of BSO depleted GSH levels and prevented the MQ- induced increase in GSH, sensitising cells to oxidative insult. In order to address the role of p53 in the response to oxidative stress, karyotypically normal p53 -/- ES cells were compared to wild -type cells. This showed that both maintenance of basal GSH levels and MQ- induction of GSH were independent of p53 status. However, a role for p53 in this response was demonstrated as the kinetics of MQ- induced apoptosis were delayed in the absence of p53. Taken together, these findings suggest that the pathways involving p53 and GSH act independently to protect against the deleterious effects of oxidative damage.Consistent with studies using a wide spectrum of other DNA damage inducing agents, loss of p53 conferred an immediate survival advantage post oxidative stress. However, the long -term clonogenic survival of p53 -/- ES cells was found to be lower than cells with an intact p53 pathway. This suggests that compensatory mechanisms exist to ensure that, in the absence of functional p53, cells bearing genetic lesions are less likely to be propagated, and furthermore that the ability to engage apoptosis does not necessarily predict long term clonogenic survival.In summary, an attempt was made to address the in vivo significance of GSH by creating a ,GCSh null strain of mice. To this end a targeting vector was generated and used in ES cells, but unfortunately this failed to produce a mutant ),GCSh allele. This thesis has also explored the relationship between oxidative damage and the cellular responses of GSH and p53 in vitro. Evidence is presented to demonstrate that, within embryonic tissues, multiple pathways operate in response to oxidative stress, and that in the absence of p53 cells are prevented from propagating

Status of LaRC HSCT high-lift research

The viewgraphs for a status report of the NASA Langley Reseach Center High Speed Civil Transport (HSCT) High-Lift Research Program are provided. A listing of available models and previous wind tunnel studies are presented. Objectives and approach of the piloted simulation program are given. The HSCT High-Lift Research plans are listed and briefly described

Low-speed wind-tunnel investigation of the flight dynamic characteristics of an advanced turboprop business/commuter aircraft configuration

An investigation was conducted to determine the low-speed flight dynamic behavior of a representative advanced turboprop business/commuter aircraft concept. Free-flight tests were conducted in the NASA Langley Research Center's 30- by 60-Foot Tunnel. In support of the free-flight tests, conventional static, dynamic, and free-to-roll oscillation tests were performed. Tests were intended to explore normal operating and post stall flight conditions, and conditions simulating the loss of power in one engine

Analysis of the Flight Motions of a Small Deployable Glider Configuration

An investigation was conducted at the request of the U.S. Air Force Avionics Laboratory to analyze the flight characteristics of a small uncontrolled glider with folding wings. The study consisted of wind-tunnel tests of an actual glider and a theoretical analysis of the performance, stability, and trimmability of the configuration

Measuring Gravitational Lensing Flexions in Abell 1689 Using an Analytic Image Model

Measuring dark matter substructure within galaxy cluster haloes is a fundamental probe of the Lambda-CDM model of structure formation. Gravitational lensing is a technique for measuring the total mass distribution which is independent of the nature of the gravitating matter, making it a vital tool for studying these dark-matter dominated objects. We present a new method for measuring weak gravitational lensing flexions, the gradients of the lensing shear field, to measure mass distributions on small angular scales. While previously published methods for measuring flexions focus on measuring derived properties of the lensed images, such as shapelet coefficients or surface brightness moments, our method instead fits a mass-sheet-transformation-invariant Analytic Image Model (AIM) to the each galaxy image. This simple parametric model traces the distortion of lensed image isophotes and constrains the flexion fields. We test the AIM method using simulated data images with realistic noise and a variety of unlensed image properties, and show that it successfully reproduces the input flexion fields. We also apply the AIM method for flexion measurement to Hubble Space Telescope observations of Abell 1689, and detect mass structure in the cluster using flexions measured with the AIM method.Comment: 44 pages, 4 figures, 3 tables. Accepted to ApJ. V2 (published version) has minor changes from V1; ApJ 736 (2011

Low-speed wind-tunnel test of a STOL supersonic-cruise fighter concept

A wind-tunnel investigation was conducted to examine the low-speed static stability and control characteristics of a 0.10 scale model of a STOL supersonic cruise fighter concept. The concept, referred to as a twin boom fighter, was designed as a STOL aircraft capable of efficient long range supersonic cruise. The configuration name is derived from the long twin booms extending aft of the engine to the twin vertical tails which support a high center horizontal tail. The propulsion system features a two dimensional thrust vectoring exhaust nozzle which is located so that the nozzle hinge line is near the aircraft center of gravity. This arrangement is intended to allow large thrust vector angles to be used to obtain significant values of powered lift, while minimizing pitching moment trim changes. Low speed stability and control information was obtained over an angle of attack range including the stall. A study of jet induced power effects was included

RXTE-PCA observations of 1A 1118--61: timing and spectral studies during an outburst

We report detailed timing and spectral analysis of RXTE-PCA data obtained from observations during the outburst of a transient X-ray pulsar 1A 1118--61 in January 2009. The pulse profile showed significant evolution during the outburst and also significant energy dependence - a double peaked profile upto 10 keV and a single peak at higher energy. We have also detected quasi-periodic oscillations (QPO) at 0.07--0.09 Hz. The rms value of the QPO is 5.2% and it shows a significant energy dependence with highest rms of 7% at 9 keV. The QPO frequency changed from 0.09 Hz to 0.07 Hz within 10 days. The magnetic field strength calculated using the QPO frequency and the X-ray luminosity is in agreement with the magnetic field strength measured from the energy of the cyclotron absorption feature detected in this source. The 3-30 keV energy spectrum over the 2009 outburst of 1A 1118--61 can be well fitted with a partial covering power-law model with a high energy cutoff and an iron fluorescence line emission. The pulse phase resolved spectral analysis shows that the partial covering and high energy cutoff model parameters have significant changes with the pulse phase.Comment: Accepted for publication in MNRA

Temporal dynamics of Prochlorococcus cells with the potential for nitrate assimilation in the subtropical Atlantic and Pacific oceans

Utilization of nitrate as a nitrogen source is broadly conserved among marine phytoplankton, yet many strains of Prochlorococcus lack this trait. Among cultured strains, nitrate assimilation has only been observed within two clades of Prochlorococcus: the high-light adapted HLII clade and the low-light adapted LLI clade. To better understand the frequency and dynamics of nitrate assimilation potential among wild Prochlorococcus, we measured seasonal changes in the abundance of cells containing the nitrate reductase gene (narB) in the subtropical North Atlantic and North Pacific oceans. At the Atlantic station, the proportion of HLII cells containing narB varied with season, with the highest frequency observed in stratified waters during the late summer, when inorganic nitrogen concentrations were lowest. The Pacific station, with more persistent stratification and lower N : P ratios, supported a perennially stable subpopulation of HLII cells containing narB. Approximately 20–50% of HLII cells possessed narB under stratified conditions at both sites. Since HLII cells dominate the total Prochlorococcus population in both ecosystems, nitrate potentially supports a significant fraction of the Prochlorococcus biomass in these waters. The abundance of LLI cells containing narB was positively correlated with nitrite concentrations at the Atlantic station. These data suggest that Prochlorococcus may contribute to the formation of primary nitrite maxima through incomplete nitrate reduction and highlight the potential for interactions between Prochlorococcus and sympatric nitrifying microorganisms. Further examination of these relationships will help clarify the selection pressures shaping nitrate utilization potential in low-light and high-light adapted Prochlorococcus.Gordon and Betty Moore Foundation (Grant GBMF495)National Science Foundation (U.S.) (OCE-1153588)National Science Foundation (U.S.) (DBI-0424599

Five-Year Cost of Dementia: Medicare

About 5.5 million older adults are living with dementia, a chronic, progressive disease characterized by severe cognitive decline. This number will likely grow significantly as the U.S. population ages, which has cost implications for the Medicare program. A full accounting of these additional expenses will help policymakers plan for them in their Medicare budgets. In this study, Norma Coe and colleagues examined survival and Medicare expenditures in older adults with and without dementia to estimate dementia’s incremental costs to Medicare in the five years after diagnosis