240 research outputs found
Cancer and non-cancer health effects from dietary toxic exposure for children and adults in California
BACKGROUND: In the absence of current cumulative dietary exposure assessments, this analysis was conducted to estimate exposure to multiple dietary contaminants for children, who are more vulnerable to toxic exposure than adults. METHODS: We estimated exposure to multiple food contaminants based on dietary data from preschool-age children (2–4 years, n=207), school-age children (5–7 years, n=157), parents of young children (n=446), and older adults (n=149). We compared exposure estimates for eleven toxic compounds (acrylamide, arsenic, lead, mercury, chlorpyrifos, permethrin, endosulfan, dieldrin, chlordane, DDE, and dioxin) based on self-reported food frequency data by age group. To determine if cancer and non-cancer benchmark levels were exceeded, chemical levels in food were derived from publicly available databases including the Total Diet Study. RESULTS: Cancer benchmark levels were exceeded by all children (100%) for arsenic, dieldrin, DDE, and dioxins. Non-cancer benchmarks were exceeded by >95% of preschool-age children for acrylamide and by 10% of preschool-age children for mercury. Preschool-age children had significantly higher estimated intakes of 6 of 11 compounds compared to school-age children (p<0.0001 to p=0.02). Based on self-reported dietary data, the greatest exposure to pesticides from foods included in this analysis were tomatoes, peaches, apples, peppers, grapes, lettuce, broccoli, strawberries, spinach, dairy, pears, green beans, and celery. CONCLUSIONS: Dietary strategies to reduce exposure to toxic compounds for which cancer and non-cancer benchmarks are exceeded by children vary by compound. These strategies include consuming organically produced dairy and selected fruits and vegetables to reduce pesticide intake, consuming less animal foods (meat, dairy, and fish) to reduce intake of persistent organic pollutants and metals, and consuming lower quantities of chips, cereal, crackers, and other processed carbohydrate foods to reduce acrylamide intake
The Prograde Orbit of Exoplanet TrES-2b
We monitored the Doppler shift of the G0V star TrES-2 throughout a transit of
its giant planet. The anomalous Doppler shift due to stellar rotation (the
Rossiter-McLaughlin effect) is discernible in the data, with a signal-to-noise
ratio of 2.9, even though the star is a slow rotator. By modeling this effect
we find that the planet's trajectory across the face of the star is tilted by
-9 +/- 12 degrees relative to the projected stellar equator. With 98%
confidence, the orbit is prograde.Comment: ApJ, in press [15 pages
Expression of heterologous proteins flanked by NS3-4A cleavage sites within the hepatitis C virus polyprotein
AbstractHepatitis C virus (HCV) contributes substantially to human morbidity and mortality world-wide. The development of HCV genomes expressing heterologous proteins has enhanced the ability to study viral infection, but existing systems have drawbacks. Recombinant viruses often require adaptive mutations to compensate for reduced viral titers, or rely on an artificial genomic organization that uncouples viral protein expression from recombinant gene expression. Here, we sought to exploit the viral polyprotein processing machinery to express heterologous proteins within the context of the HCV polyprotein. We show that HCV genotypes 2a and 1b permit insertion of reporter proteins between NS5A and NS5B with minimal impact on viral fitness. Using this strategy we constructed reporter genomes exhibiting a wide dynamic range, simplifying analysis of HCV infection in primary hepatocytes. Expression of heterologous proteins within the HCV genome offers new opportunities to analyze HCV infection in experimental systems without perturbing functions of individual viral proteins
Recapitulation of the hepatitis C virus life-cycle in engineered murine cell lines
AbstractHepatitis C virus (HCV) remains a major medical problem. In-depth study of HCV pathogenesis and immune responses is hampered by the lack of suitable small animal models. The narrow host range of HCV remains incompletely understood. We demonstrate that the entire HCV life-cycle can be recapitulated in mouse cells. We show that antiviral signaling interferes with HCV RNA replication in mouse cells. We were able to infect mouse cells expressing human CD81 and occludin (OCLN)—the minimal set of entry factor factors required for HCV uptake into mouse cells. Infected mouse cells sustain HCV RNA replication in the presence of miR122 and release infectious particles when mouse apoE is supplied. Our data demonstrate that the barriers of HCV interspecies transmission can be overcome by engineering a suitable cellular environment and provide a blue-print towards constructing a small animal model for HCV infection
Spin-Orbit Alignment for the Eccentric Exoplanet HD 147506b
The short-period exoplanet HD 147506b (also known as HAT-P-2b) has an eccentric orbit, raising the possibility that it migrated through planet-planet scattering or Kozai oscillations accompanied by tidal dissipation. Either of these scenarios could have significantly tilted the orbit relative to the host star's equatorial plane. Here we present spectroscopy of a transit of HD 147506b and assess the spin-orbit alignment via the Rossiter-McLaughlin effect. We find the angle between the sky projections of the stellar spin axis and orbital axis to be aligned within 14°. Thus, we find no corroborating evidence for scattering or Kozai migration, although these scenarios cannot be ruled out with the present data
Measurement of Spin-Orbit Alignment in an Extrasolar Planetary System
We determine the stellar, planetary, and orbital properties of the transiting planetary system HD 209458 through a joint analysis of high-precision radial velocities, photometry, and timing of the secondary eclipse. Of primary interest is the strong detection of the Rossiter-McLaughlin effect, the alteration of photospheric line profiles that occurs because the planet occults part of the rotating surface of the star. We develop a new technique for modeling this effect and use it to determine the inclination of the planetary orbit relative to the apparent stellar equator (λ = -4º.4 ± 1º.4), and the line-of-sight rotation speed of the star (v sin /_★ = 4.70 ± 0.16 km s^(-1)). The uncertainty in these quantities has been reduced by an order of magnitude relative to the pioneering measurements by Queloz and collaborators. The small but nonzero misalignment is probably a relic of the planet formation epoch, because the expected timescale for tidal coplanarization is larger than the age of the star. Our determination of v sin /★ is a rare case in which rotational line broadening has been isolated from other broadening mechanisms
Measurement of the Spin-Orbit Alignment in the Exoplanetary System HD 189733
We present spectroscopy of a transit of the exoplanet HD 189733b. By modeling
the Rossiter-McLaughlin effect (the anomalous Doppler shift due to the partial
eclipse of the rotating stellar surface), we find the angle between the sky
projections of the stellar spin axis and orbit normal to be lambda = -1.4 +/-
1.1 deg. This is the third case of a ``hot Jupiter'' for which lambda has been
measured. In all three cases lambda is small, ruling out random orientations
with 99.96% confidence, and suggesting that the inward migration of hot
Jupiters generally preserves spin-orbit alignment.Comment: ApJ Letters, in pres
Variable Sodium Absorption in a Low-Extinction Type Ia Supernova
Recent observations have revealed that some Type Ia supernovae exhibit
narrow, time-variable Na I D absorption features. The origin of the absorbing
material is controversial, but it may suggest the presence of circumstellar gas
in the progenitor system prior to the explosion, with significant implications
for the nature of the supernova progenitors. We present the third detection of
such variable absorption, based on six epochs of high-resolution spectroscopy
of the Type Ia supernova SN 2007le from Keck and the HET. The data span ~3
months, from 5 days before maximum light to 90 days after maximum. We find that
one component of the Na D absorption lines strengthened significantly with
time, indicating a total column density increase of ~2.5 x 10^12 cm^-2. The
changes are most prominent after maximum light rather than at earlier times
when the UV flux from the SN peaks. As with SN 2006X, we detect no change in
the Ca II H&K lines over the same time period, rendering line-of-sight effects
improbable and suggesting a circumstellar origin for the absorbing material.
Unlike the previous two SNe exhibiting variable absorption, SN 2007le is not
highly reddened (E_B-V = 0.27 mag), also pointing toward circumstellar rather
than interstellar absorption. Photoionization models show that the data are
consistent with a dense (10^7 cm^-3) cloud or clouds of gas located ~0.1 pc
from the explosion. These results broadly support the single-degenerate
scenario previously proposed to explain the variable absorption, with mass loss
from a nondegenerate companion star responsible for providing the circumstellar
gas. We also present tentative evidence for narrow Halpha emission associated
with the SN, which will require followup observations at late times to confirm.
[abridged]Comment: 16 pages, 10 figures (8 in color), 5 tables. Accepted for publication
in Ap
Measurement of the Spin-Orbit Angle of Exoplanet HAT-P-1b
We present new spectroscopic and photometric observations of the HAT-P-1
planetary system. Spectra obtained during three transits exhibit the
Rossiter-McLaughlin effect, allowing us to measure the angle between the sky
projections of the stellar spin axis and orbit normal, \lambda = 3.7 +/- 2.1
degrees. The small value of \lambda for this and other systems suggests that
the dominant planet migration mechanism preserves spin-orbit alignment. Using
two new transit light curves, we refine the transit ephemeris and reduce the
uncertainty in the orbital period by an order of magnitude. We find a upper
limit on the orbital eccentricity of 0.067, with 99% confidence, by combining
our new radial-velocity measurements with those obtained previously.Comment: 28 total pages, 4 figures, 4 tables, ApJ Accepte
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