Investigation of Novel Functions for DNA Damage Response and Repair Proteins in Escherichia coli and Humans

Endogenous and exogenous agents that can damage DNA are a constant threat to genome stability in all living cells. In response, cells have evolved an array of mechanisms to repair DNA damage or to eliminate the cells damaged beyond repair. One of these mechanisms is nucleotide excision repair (NER) which is the major repair pathway responsible for removing a wide variety of bulky DNA lesions. Deficiency, or mutation, in one or several of the NER repair proteins is responsible for many diseases, including cancer. Prokaryotic NER involves only three proteins to recognize and incise a damaged site, while eukaryotic NER requires more than 25 proteins to efficiently recognize and incise a damaged site. XPC-RAD23B (XPC) is the damage recognition factor in eukaryotic global genome NER. The association rate of XPC to damaged DNA has been extensively studied; however, our data suggests that the dissociation of the XPC-DNA complex is the rate-limiting step in NER. The factor that verifies DNA-damage downstream of XPC is XPA. XPA also has been implicated in binding of ds-ssDNA junctions and has been found to bind at or near double-strand break sites in the premature aging syndrome Hutchinson-Gilford progeria (HGPS). This role for XPA is outside of its known function in NER and suggests that XPA may bind at collapsed replication forks in HGPS that are unprotected due to a lack of binding by replication proteins. Along with XPC and XPA, ataxia telangiectasia and Rad3-related (ATR) is activated in response to DNA damage and initiates the cell cycle checkpoint pathway to rescue cells from genomic instability. We found that ATR functions outside of its known role in the checkpoint signaling cascade. Our data demonstrate that ATR can rescue cells from apoptosis by inhibiting cytochrome c release at the mitochondria though direct interaction with the outer mitochondrial membrane and the proapoptotic protein tBid. The role of ATR in apoptosis is regulated by Pin1, which can change the structure of ATR at the backbone level. All of the results presented here suggest novel roles for DNA repair proteins in the maintenance of genome stability

The Implications of M Dwarf Flares on the Detection and Characterization of Exoplanets at Infrared Wavelengths

We present the results of an observational campaign which obtained high time cadence, high precision, simultaneous optical and IR photometric observations of three M dwarf flare stars for 47 hours. The campaign was designed to characterize the behavior of energetic flare events, which routinely occur on M dwarfs, at IR wavelengths to milli-magnitude precision, and quantify to what extent such events might influence current and future efforts to detect and characterize extrasolar planets surrounding these stars. We detected and characterized four highly energetic optical flares having U-band total energies of ~7.8x10^30 to ~1.3x10^32 ergs, and found no corresponding response in the J, H, or Ks bandpasses at the precision of our data. For active dM3e stars, we find that a ~1.3x10^32 erg U-band flare (delta Umax ~1.5 mag) will induce <8.3 (J), <8.5 (H), and <11.7 (Ks) milli-mags of a response. A flare of this energy or greater should occur less than once per 18 hours. For active dM4.5e stars, we find that a ~5.1x10^31 erg U-band flare (delta Umax ~1.6 mag) will induce <7.8 (J), <8.8 (H), and <5.1 (Ks) milli-mags of a response. A flare of this energy or greater should occur less than once per 10 hours. No evidence of stellar variability not associated with discrete flare events was observed at the level of ~3.9 milli-mags over 1 hour time-scales and at the level of ~5.6 milli-mags over 7.5 hour time-scales. We therefore demonstrate that most M dwarf stellar activity and flares will not influence IR detection and characterization studies of M dwarf exoplanets above the level of ~5-11 milli-mags, depending on the filter and spectral type. We speculate that the most energetic megaflares on M dwarfs, which occur at rates of once per month, are likely to be easily detected in IR observations with sensitivity of tens of milli-mags.Comment: Accepted in Astronomical Journal, 17 pages, 6 figure

Acute Ingestion Of L-Arginine Alpha-Ketoglutarate Fails To Improve Muscular Strength And Endurance In ROTC Cadets

International Journal of Exercise Science 6(2) : 91-97, 2013. L-Arginine Alpha-Ketoglutarate (AAKG) is purported to stimulate the release of nitric oxide, and is suggested to facilitate muscular performance by increasing blood flow and increase oxygen and nutrient delivery to the working muscle. However, the ergogenic benefit of AAKG during resistance exercise has not been established. Therefore the purpose of this study was to investigate the effects of acute AAKG ingestion in active ROTC Cadets on measures of one-repetition maximal strength (1RM) and muscular endurance. Nineteen apparently healthy males ingested either AAKG (3 g) or a placebo 45 minutes prior to resistance testing in a randomized, double-blind crossover design. Initially, blood lactate (BLA) was obtained followed by 1RM testing on the barbell bench press and leg press. Upon determination of 1RM, participants completed repetitions to failure at 60% of 1RM. Blood lactate measures were immediately taken following the final repetition. Analysis revealed no significant differences between the conditions for bench press 1RM. Additionally, there were no differences between conditions for 1RM leg press, or for number of repetitions performed for the bench press or leg press. Blood lactate values did increase significantly from baseline to post-bench press in both the AAKG (t33 = 7.56, p \u3c 0.01) and placebo conditions (t33 = 8.45, p \u3c 0.01). Further, BLA lactate levels were also significantly greater post leg-press in the AAKG (t33 = 9.23, p \u3c 0.01) and placebo (t33 = 8.10, p \u3c 0.01). The results indicate that acute AAKG supplementation provides no ergogenic benefit in this study

A Mouse Model of Harlequin Ichthyosis Delineates a Key Role for Abca12 in Lipid Homeostasis

Harlequin Ichthyosis (HI) is a severe and often lethal hyperkeratotic skin disease caused by mutations in the ABCA12 transport protein. In keratinocytes, ABCA12 is thought to regulate the transfer of lipids into small intracellular trafficking vesicles known as lamellar bodies. However, the nature and scope of this regulation remains unclear. As part of an original recessive mouse ENU mutagenesis screen, we have identified and characterised an animal model of HI and showed that it displays many of the hallmarks of the disease including hyperkeratosis, loss of barrier function, and defects in lipid homeostasis. We have used this model to follow disease progression in utero and present evidence that loss of Abca12 function leads to premature differentiation of basal keratinocytes. A comprehensive analysis of lipid levels in mutant epidermis demonstrated profound defects in lipid homeostasis, illustrating for the first time the extent to which Abca12 plays a pivotal role in maintaining lipid balance in the skin. To further investigate the scope of Abca12's activity, we have utilised cells from the mutant mouse to ascribe direct transport functions to the protein and, in doing so, we demonstrate activities independent of its role in lamellar body function. These cells have severely impaired lipid efflux leading to intracellular accumulation of neutral lipids. Furthermore, we identify Abca12 as a mediator of Abca1-regulated cellular cholesterol efflux, a finding that may have significant implications for other diseases of lipid metabolism and homeostasis, including atherosclerosis

Smoke gets in your eyes:what is sociological about cigarettes?

Contemporary public health approaches increasingly draw attention to the unequal social distribution of cigarette smoking. In contrast, critical accounts emphasize the importance of smokers’ situated agency, the relevance of embodiment and how public health measures against smoking potentially play upon and exacerbate social divisions and inequality. Nevertheless, if the social context of cigarettes is worthy of such attention, and sociology lays a distinct claim to understanding the social, we need to articulate a distinct, positive and systematic claim for smoking as an object of sociological enquiry. This article attempts to address this by situating smoking across three main dimensions of sociological thinking: history and social change; individual agency and experience; and social structures and power. It locates the emergence and development of cigarettes in everyday life within the project of modernity of the nineteenth and twentieth centuries. It goes on to assess the habituated, temporal and experiential aspects of individual smoking practices in everyday lifeworlds. Finally, it argues that smoking, while distributed in important ways by social class, also works relationally to render and inscribe it

ATR Prevents Ca\u3csup\u3e2+\u3c/sup\u3e Overload-Induced Necrotic Cell Death Through Phosphorylation-Mediated Inactivation of PARP1 Without DNA Damage Signaling

Hyperactivation of PARP1 is known to be a major cause of necrotic cell death by depleting NAD+/ATP pools during Ca2+ overload which is associated with many ischemic diseases. However, little is known about how PARP1 hyperactivity is regulated during calcium overload. In this study we show that ATR kinase, well known for its role in DNA damage responses, suppresses ionomycin, glutamate, or quinolinic acid-induced necrotic death of cells including SH-SY5Y neuronal cells. We found that the inhibition of necrosis requires the kinase activity of ATR. Specifically, ATR binds to and phosphorylates PARP1 at Ser179 after the ionophore treatments. This site-specific phosphorylation inactivates PARP1, inhibiting ionophore-induced necrosis. Strikingly, all of this occurs in the absence of detectable DNA damage and signaling up to 8 hours after ionophore treatment. Furthermore, little AIF was released from mitochondria/cytoplasm for nuclear import, supporting the necrotic type of cell death in the early period of the treatments. Our results reveal a novel ATR-mediated anti-necrotic mechanism in the cellular stress response to calcium influx without DNA damage signaling

Observation of the spin-charge thermal isolation of ferromagnetic Ga_{0.94}Mn_{0.06}As by time-resolved magneto-optical measurement

The dynamics of magnetization under femtosecond optical excitation is studied in a ferromagnetic semiconductor Ga_{0.94}Mn_{0.06}As with a time-resolved magneto-optical Kerr effect measurement with two color probe beams. The transient reflectivity change indicates the rapid rise of the carrier temperature and relaxation to a quasi-thermal equilibrium within 1 ps, while a very slow rise of the spin temperature of the order of 500ps is observed. This anomalous behavior originates from the thermal isolation between the charge and spin systems due to the spin polarization of carriers (holes) contributing to ferromagnetism. This constitutes experimental proof of the half-metallic nature of ferromagnetic Ga_{0.94}Mn_{0.06}As arising from double exchange type mechanism originates from the d-band character of holes

The Atacama Cosmology Telescope: The LABOCA/ACT Survey of Clusters at All Redshifts

We present a multi-wavelength analysis of eleven Sunyaev Zel'dovich effect (SZE)-selected galaxy clusters (ten with new data) from the Atacama Cosmology Telescope (ACT) southern survey. We have obtained new imaging from the Large APEX Bolometer Camera (345GHz; LABOCA) on the Atacama Pathfinder EXperiment (APEX) telescope, the Australia Telescope Compact Array (2.1GHz; ATCA), and the Spectral and Photometric Imaging Receiver (250, 350, and $500\,\rm\mu m$; SPIRE) on the Herschel Space Observatory. Spatially-resolved 345GHz SZE increments with integrated S/N > 5 are found in six clusters. We compute 2.1GHz number counts as a function of cluster-centric radius and find significant enhancements in the counts of bright sources at projected radii $\theta < \theta_{2500}$. By extrapolating in frequency, we predict that the combined signals from 2.1GHz-selected radio sources and 345GHz-selected SMGs contaminate the 148GHz SZE decrement signal by ~5% and the 345GHz SZE increment by ~18%. After removing radio source and SMG emission from the SZE signals, we use ACT, LABOCA, and (in some cases) new Herschel SPIRE imaging to place constraints on the clusters' peculiar velocities. The sample's average peculiar velocity relative to the cosmic microwave background is $153\pm 383\,\rm km\,s^{-1}$.Comment: 19 pages, 11 figures, Accepted for Publication in The Astrophysical Journa

The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey

We present a catalog of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 GHz and/or 218 GHz in the 2008 Southern survey. Flux densities span 14-1700 mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two sub-populations: 167 radio galaxies powered by central active galactic nuclei (AGN), and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97% of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogs. When combined with flux densities from the Australian Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148 GHz, with the trend continuing to 218 GHz. The ACT dust-dominated source population has a median spectral index of 3.7+0.62-0.86, and includes both local galaxies and sources with redshifts as great as 5.6. Dusty sources with no counterpart in existing catalogs likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.Comment: 13 pages, 8 figures, 4 table

A Study on the Effects of Ball Defects on the Fatigue Life in Hybrid Bearings

Hybrid ball bearings using silicon nitride ceramic balls with steel rings are increasingly being used in space mechanism applications due to their high wear resistance and long rolling contact fatigue life. However, qualitative and quantitative reports of the effects of ball defects that cause early fatigue failure are rare. We report on our approach to study these effects. Our strategy includes characterization of defects encountered in use, generation of similar defects in a laboratory setting, execution of full-scale bearing tests to obtain lifetimes, post-test characterization, and related finite-element modeling to understand the stress concentration of these defects. We have confirmed that at least one type of defect of appropriate size can significantly reduce fatigue life. Our method can be used to evaluate other defects as they occur or are encountered