142 research outputs found
Murine terminal deoxynucleotidyl transferase: cellular distribution and response to cortisone
The mouse thymus contains two forms of terminal deoxynucleotidyl transferase (TdT) which are distinguishable by the salt concentration necessary to elute them from a phosphocellulose column, by their distrubtion among the thymocyte subpopulations, and by their sensitivity to cortisone treatment. In the whole thymus the later eluting peak (peak II) is the predominant one with about 3-10% of the total activity appearing in peak I. Both peak I and peak II activities are most sensitively assayed by the polymerization of dGMP onto an oligo(dA) primer. The minor population of thymocytes which is less dense and cortisone-resistant contains a higher specific activity of peak I TdT. The majority of TdT activity is, however, found in the major population of thymocytes which occurs in the center region of a bovine serum albumin gradient and is cortisone-sensitive. A very low level of an activity indistinguishable from peak II TdT activity is also detected in the mouse bone marrow. Other tissues, such as spleen, liver, heart, and brain lack detectable amounts of TdT activity
Biosynthesis of Murine Terminal Deoxynucleotidyltransferase
An immunoprecipitation assay for measuring synthesis of murine terminal deoxynucleotidyltransferase (EC 2.7.7.31) has been developed using rabbit antiserum to calf terminal transferase. The antiserum precipitates a single Mr = 60,000 polypeptide (TdT-60) from all cell lines and tissues that contain enzymologically demonstrable terminal transferase. This polypeptide is not precipitated from labeled extracts of cells that lack terminal transferase by enzymological criteria. TdT-60 fractionates with terminal transferase during phosphocellulose chromatography and sediments with it in a sucrose gradient. TdT-60 is not detectably processed to lower molecular weight polypeptides, and terminal transferase activity sediments as a Mr = 60,000 activity; thus, we believe it to be the active form of terminal transferase. Using this assay we have demonstrated that terminal transferase is synthesized in both the murine thymus and the bone marrow at a rate proportional to its biochemically measured steady state level. After cortisone treatment of mice, the Mr = 60,000 polypeptide disappears from the thymus and then reappears as the thymus begins to be repopulated
Cloning of terminal transferase cDNA by antibody screening
A cDNA library was prepared from a terminal deoxynucleotidyltransferase-containing thymoma in the phage vector λgt11. By screening plaques with anti-terminal transferase antibody, positive clones were identified of which some had ÎČ-galactosidase-cDNA fusion proteins identifiable after electrophoretic fractionation by immunoblotting with anti-terminal transferase antibody. The predominant class of cross-hybridizing clones was determined to represent cDNA for terminal transferase by showing that one representative clone hybridized to a 2200-nucleotide mRNA in close-matched enzyme-positive but not to enzyme-negative cells and that the cDNA selected a mRNA that translated to give a protein of the size and antigenic characteristics of terminal transferase. Only a small amount of genomic DNA hybridized to the longest available clone, indicating that the sequence is virtually unique in the mouse genome
Maximizing precision in saturation-limited absorption measurements
Quantum fluctuations in the intensity of an optical probe is noise which
limits measurement precision in absorption spectroscopy. Increased probe power
can offer greater precision, however, this strategy is often constrained by
sample saturation. Here, we analyse measurement precision for a generalised
absorption model in which we account for saturation and explore its effect on
both classical and quantum probe performance. We present a classical
probe-sample optimisation strategy to maximise precision and find that optimal
probe powers always fall within the saturation regime. We apply our
optimisation strategy to two examples, high-precision Doppler broadened
thermometry and an absorption spectroscopy measurement of Chlorophyll A. We
derive a limit on the maximum precision gained from using a non-classical probe
and find a strategy capable of saturating this bound. We evaluate
amplitude-squeezed light as a viable experimental probe state and find it
capable of providing precision that reaches to within > 85% of the ultimate
quantum limit with currently available technology.Comment: 12 pages and 5 figure
Depression Outcomes in Adults Attending Family Practice Were Not Improved by Screening, Stepped-Care, or Online CBT during a 12-Week Study when Compared to Controls in a Randomized Trial
Polychlorinated Biphenyl (PCB) Exposure and Diabetes: Results from the Anniston Community Health Survey
Background: Polychlorinated biphenyls (PCBs) manufactured in Anniston, Alabama, from 1929 to 1971 caused significant environmental contamination. The Anniston population remains one of the most highly exposed in the world
Using Nutrition for Intervention and Prevention against Environmental Chemical Toxicity and Associated Diseases
BACKGROUND: Nutrition and lifestyle are well-defined modulators of chronic diseases. Poor dietary habits (such as high intake of processed foods rich in fat and low intake of fruits and vegetables), as well as a sedentary lifestyle clearly contribute to todayâs compromised quality of life in the United States. It is becoming increasingly clear that nutrition can modulate the toxicity of environmental pollutants. OBJECTIVES: Our goal in this commentary is to discuss the recommendation that nutrition should be considered a necessary variable in the study of human disease associated with exposure to environmental pollutants. DISCUSSION: Certain diets can contribute to compromised health by being a source of exposure to environmental toxic pollutants. Many of these pollutants are fat soluble, and thus fatty foods often contain higher levels of persistent organics than does vegetable matter. Nutrition can dictate the lipid milieu, oxidative stress, and antioxidant status within cells. The modulation of these parameters by an individualâs nutritional status may have profound affects on biological processes, and in turn influence the effects of environmental pollutants to cause disease or dysfunction. For example, potential adverse health effects associated with exposure to polychlorinated biphenyls may increase as a result of ingestion of certain dietary fats, whereas ingestion of fruits and vegetables, rich in antioxidant and anti-inflammatory nutrients or bioactive compounds, may provide protection. CONCLUSIONS: We recommend that future directions in environmental health research explore this nutritional paradigm that incorporates a consideration of the relationships between nutrition and lifestyle, exposure to environmental toxicants, and disease. Nutritional interventions may provide the most sensible means to develop primary prevention strategies of diseases associated with many environmental toxic insults
"Ordinary, the same as anywhere else": notes on the management of spoiled identity in 'marginal' middle class neighbourhoods
Urban sociologists are becoming increasingly interested in neighbourhood as a source of middle-class identity. Particular emphasis is currently being given to two types of middle-class neighbourhood; gentrified urban neighbourhoods of âdistinctionâ and inconspicuous âsuburban landscapes of privilegeâ. However, there has been a dearth of work on âmarginalâ middle-class neighbourhoods that are similarly âinconspicuousâ rather than distinctive, but less exclusive, thus containing sources of âspoiled identityâ. This article draws on data gathered from two âmarginalâ middleclass neighbourhoods that contained a particular source of âspoiled identityâ: social renters. Urban sociological analyses of neighbour responses to these situations highlight a process of dis-identification with the maligned object, which exacerbates neighbour differences. Our analysis of data from the âmarginalâ middle-class neighbourhoods suggests something entirely different and Goffmanesque. This entailed the management of spoiled identity, which emphasized similarities rather than differences between neighbours.</p
Infrared and kinematic properties of the substellar object G 196-3B
We report unusual near- and mid-infrared photometric properties of G 196-3 B,
the young substellar companion at 16 arcsec from the active M2.5-type star G
196-3 A, using data taken with the IRAC and MIPS instruments onboard Spitzer. G
196-3 B shows markedly redder colors at all wavelengths from 1.6 up to 24
micron than expected for its spectral type, which is determined at L3 from
optical and near-infrared spectra. We discuss various physical scenarios to
account for its reddish nature, and conclude that a low-gravity atmosphere with
enshrouded upper atmospheric layers and/or a warm dusty disk/envelope provides
the most likely explanations, the two of them consistent with an age in the
interval 20-300 Myr. We also present new and accurate separate proper motion
measurements for G 196-3 A and B confirming that both objects are
gravitationally linked and share the same motion within a few mas/yr. After
integration of the combined spectrophotometric spectral energy distributions,
we obtain that the difference in the bolometric magnitudes of G 196-3 A and B
is 6.15 +/- 0.10 mag. Kinematic consideration of the Galactic space motions of
the system for distances in the interval 15-30 pc suggests that the pair is a
likely member of the Local Association, and that it lay near the past positions
of young star clusters like alpha Persei less than 85 Myr ago, where the binary
might have originated. At these young ages, the mass of G 196-3 B would be in
the range 12-25 Mjup, close to the frontier between planets and brown dwarfs.Comment: Accepted for publication in ApJ
The low level of debris disk activity at the time of the Late Heavy Bombardment: a Spitzer study of Praesepe
We present 24 micron photometry of the intermediate-age open cluster
Praesepe. We assemble a catalog of 193 probable cluster members that are
detected in optical databases, the Two Micron All Sky Survey (2MASS), and at 24
micron, within an area of ~ 2.47 square degrees. Mid-IR excesses indicating
debris disks are found for one early-type and for three solar-type stars.
Corrections for sampling statistics yield a 24 micron excess fraction (debris
disk fraction) of 6.5 +- 4.1% for luminous and 1.9 +- 1.2% for solar-type
stars. The incidence of excesses is in agreement with the decay trend of debris
disks as a function of age observed for other cluster and field stars. The
values also agree with those for older stars, indicating that debris generation
in the zones that emit at 24 micron falls to the older 1-10 Gyr field star
sample value by roughly 750 Myr.
We discuss our results in the context of previous observations of excess
fractions for early- and solar-type stars. We show that solar-type stars lose
their debris disk 24 micron excesses on a shorter timescale than early-type
stars. Simplistic Monte Carlo models suggest that, during the first Gyr of
their evolution, up to 15-30% of solar-type stars might undergo an orbital
realignment of giant planets such as the one thought to have led to the Late
Heavy Bombardment, if the length of the bombardment episode is similar to the
one thought to have happened in our Solar System.
In the Appendix, we determine the cluster's parameters via boostrap Monte
Carlo isochrone fitting, yielding an age of 757 Myr (+- 36 Myr at 1 sigma
confidence) and a distance of 179 pc (+- 2 pc at 1 sigma confidence), not
allowing for systematic errors.Comment: 22 pages, 14 figures, 9 tables, emulateapj format; Accepted for
publication in The Astrophysical Journa
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