298 research outputs found
Determination of Methylarginines in Infant Plasma by CE-LIF
Methylarginines (MAs) are a class of nitric oxide synthase inhibitors that have been implicated in respiratory complications of critically ill infants. This paper describes the development of an analytical method to measure these compounds in the plasma of newborns using capillary electrophoresis (CE). The CE separation method was optimized to enable complete baseline resolution of the four MA analogues of interest. Sample preparation concerns for infant-derived samples were addressed by validating a heat-assisted extraction method for the analysis of low volume (≤100 µL) samples from a plasma matrix. It was determined that the sample matrix (plasma versus serum) did not affect the measured MA concentrations, while extracting smaller volumes of plasma that underwent heat-induced gelation afforded higher MA recoveries than larger volume samples. These methods were then applied to blood samples collected from infants housed in the neonatal intensive care unit. It was discovered that these newborns had significantly elevated concentrations of MAs at younger ages (< 6 months) while amounts were similar between infants 6 months old and adults. The data are preliminary, but demonstrate an interesting age dependence on the concentrations of these nitric oxide inhibitors, which has not been previously reported
Optimization of the Separation of NDA-Derivatized Methylarginines by Capillary and Microchip Electrophoresis
The methylated arginines (MAs) monomethylarginine (MMA), asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA) have been shown to be independent predictors of cardiovascular disease. This article describes progress regarding the development of an analytical method capable of rapidly analyzing MAs using capillary electrophoresis (CE) and microchip electrophoresis (MCE) with laser-induced fluorescence (LIF) detection. Several parameters including buffer composition and separation voltage were optimized to achieve an ideal separation. The analytes of interest were derivatized with naphthalene-2,3-dicarboxaldehyde (NDA) to produce fluorescent 1-cyanobenz[f]isoindole (CBI) derivatives and then subjected to CE analysis. Baseline resolution of SDMA, ADMA, MMA, and arginine was achieved in less than 8 min. The limits of detection for SDMA, ADMA, MMA, and arginine were determined to be 15, 20, 25, and 5 nM, respectively, which are well below the expected plasma concentrations. The CE separation method was then transferred to a glass MCE device with LIF detection. MAs were baseline resolved in 3 min on-chip using a 14 cm separation channel with detection limits of approximately 10 nM for each species. To the best of the authors’ knowledge, this is the first report of the separation of MAs by MCE
Feeding of soy protein isolate to rats during pregnancy and lactation suppresses formation of aberrant crypt foci in their progeny's colons: interaction of diet with fetal alcohol exposure
Soy protein isolate (SPI) in the diet may inhibit colon tumorigenesis. We examined azoxymethane (AOM)-induced aberrant crypt foci (ACF) in male rats in relation to lifetime, pre-weaning, or post-weaning dietary exposure to SPI and also within the context of fetal alcohol exposure. Pregnant Sprague Dawley rats were fed AIN-93G diets containing casein (20%, the control diet) or SPI (20%) as the sole protein source starting on gestation day 4 (GD 4). Progeny were weaned on postnatal day (PND) 21 to the same diet as their dams and were fed this diet until termination of the experiment at PND 138. Rats received AOM on PND 89 and 96. Lifetime (GD 4 to PND 138) feeding of SPI led to reduced frequency of ACF with 4 or more crypts in the distal colon. Progeny of dams fed SPI only during pregnancy and lactation or progeny fed SPI only after weaning exhibited similarly reduced frequency of large ACF in distal colon. Number of epithelial cells, in the distal colon, undergoing apoptosis was unaffected by diet. SPI reduced weight gain and adiposity, but these were not correlated with fewer numbers of large ACF. Lifetime SPI exposure similarly inhibited development of large ACF in Sprague Dawley rats whose dams were exposed to ethanol during pregnancy. In summary, feeding of SPI to rat dams during pregnancy and lactation suppresses numbers of large ACF in their progeny, implying a long-term or permanent change elicited by the maternal diet. Moreover, results support the use of ACF as an intermediate endpoint for elucidating effects of SPI and its biochemical constituents in colon cancer prevention in rats
The properties of the inner disk around HL Tau: Multi-wavelength modeling of the dust emission
We conducted a detailed radiative transfer modeling of the dust emission from
the circumstellar disk around HL Tau. The goal of our study is to derive the
surface density profile of the inner disk and its structure. In addition to the
Atacama Large Millimeter/submillimeter Array images at Band 3 (2.9mm), Band 6
(1.3mm), and Band 7 (0.87mm), the most recent Karl G. Jansky Very Large Array
(VLA) observations at 7mm were included in the analysis. A simulated annealing
algorithm was invoked to search for the optimum model. The radiative transfer
analysis demonstrates that most radial components (i.e., >6AU) of the disk
become optically thin at a wavelength of 7mm, which allows us to constrain, for
the first time, the dust density distribution in the inner region of the disk.
We found that a homogeneous grain size distribution is not sufficient to
explain the observed images at different wavelengths simultaneously, while
models with a shallower grain size distribution in the inner disk work well. We
found clear evidence that larger grains are trapped in the first bright ring.
Our results imply that dust evolution has already taken place in the disk at a
relatively young (i.e., ~1Myr) age. We compared the midplane temperature
distribution, optical depth, and properties of various dust rings with those
reported previously. Using the Toomre parameter, we briefly discussed the
gravitational instability as a potential mechanism for the origin of the dust
clump detected in the first bright ring via the VLA observations.Comment: Accepted for publication in A&A (10 pages
The VLTI/MIDI survey of massive young stellar objects - Sounding the inner regions around intermediate- and high-mass young stars using mid-infrared interferometry
We aim to characterize the distribution and composition of circumstellar
material around young massive stars, and to investigate exactly which physical
structures in these objects are probed by long-baseline mid-infrared
interferometric observations. We used the two-telescope interferometric
instrument MIDI of the Very Large Telescope Interferometer of the European
Southern Observatory to observe a sample of 24 intermediate- and high-mass
young stellar objects in the N band (8-13 micron). We had successful fringe
detections for 20 objects, and present spectrally-resolved correlated fluxes
and visibility levels for projected baselines of up to 128 m. We fit the
visibilities with geometric models to derive the sizes of the emitting regions,
as well as the orientation and elongation of the circumstellar material.
Fourteen objects in the sample show the 10 micron silicate feature in
absorption in the total and correlated flux spectra. For 13 of these objects,
we were able to fit the correlated flux spectra with a simple absorption model,
allowing us to constrain the composition and absorptive properties of the
circumstellar material. Nearly all of the massive young stellar objects
observed show significant deviations from spherical symmetry at mid-infrared
wavelengths. In general, the mid-infrared emission can trace both disks and
outflows, and in many cases it may be difficult to disentangle these components
on the basis of interferometric data alone, because of the sparse spatial
frequency coverage normally provided by current long-baseline interferometers.
For the majority of the objects in this sample, the absorption occurs on
spatial scales larger than those probed by MIDI. Finally, the physical extent
of the mid-infrared emission around these sources is correlated with the total
luminosity, albeit with significant scatter.Comment: 36 pages, 22 figures. Accepted to Astronomy and Astrophysic
The Radial Distribution of Dust Particles in the HL Tau Disk from ALMA and VLA Observations
Understanding planet formation requires one to discern how dust grows in protoplanetary disks. An important parameter to measure in disks is the maximum dust grain size present. This is usually estimated through measurements of the dust opacity at different millimeter wavelengths assuming optically thin emission and dust opacity dominated by absorption. However, Atacama Large Millimeter/submillimeter Array (ALMA) observations have shown that these assumptions might not be correct in the case of protoplanetary disks, leading to overestimation of particle sizes and to underestimation of the disk\u27s mass. Here, we present an analysis of high-quality ALMA and Very Large Array images of the HL Tau protoplanetary disk, covering a wide range of wavelengths, from 0.8 mm to 1 cm, and with a physical resolution of ~7.35 au. We describe a procedure to analyze a set of millimeter images without any assumption about the optical depth of the emission, and including the effects of absorption and scattering in the dust opacity. This procedure allows us to obtain the dust temperature, the dust surface density, and the maximum particle size at each radius. In the HL Tau disk, we found that particles have already grown to a few millimeters in size. We detect differences in the dust properties between dark and bright rings, with dark rings containing low dust density and small dust particles. Different features in the HL Tau disk seem to have different origins. Planet–disk interactions can explain substructure in the external half of the disk, but the internal rings seem to be associated with the presence of snow lines of several molecules
Efficacy Of European Starling Control To Reduce Salmonella Enterica Contamination In A Concentrated Animal Feeding Operation In The Texas Panhandle
Background: European starlings (Sturnus vulgaris) are an invasive bird species known to cause damage to plant and animal agriculture. New evidence suggests starlings may also contribute to the maintenance and spread of diseases within livestock facilities. Identifying and mitigating the risk pathways that contribute to disease in livestock is necessary to reduce production losses and contamination of human food products. To better understand the impact starlings have on disease transmission to cattle we assessed the efficacy of starling control as a tool to reduce Salmonella enterica within a concentrated animal feeding operation. We matched a large facility, slated for operational control using DRC-1339 (3-chloro-4-methylaniline hydrochloride, also 3-chloro ptoluidine hydrochloride, 3-chloro-4-methylaniline), with a comparable reference facility that was not controlling birds. In both facilities, we sampled cattle feed, cattle water and cattle feces for S. enterica before and after starling control operations. Results: Within the starling-controlled CAFO, detections of S. enterica contamination disappeared from feed bunks and substantially declined within water troughs following starling control operations. Within the reference facility, detections of S. enterica contamination increased substantially within feed bunks and water troughs. Starling control was not observed to reduce prevalence of S. enterica in the cattle herd. Following starling control operations, herd prevalence of S. enterica increased on the reference facility but herd prevalence of S. enterica on the starling-controlled CAFO stayed at pretreatment levels. Conclusions: Within the starling-controlled facility detections of S. enterica disappeared from feed bunks and substantially declined within water troughs following control operations. Since cattle feed and water are obvious routes for the ingestion of S. enterica, starling control shows promise as a tool to help livestock producers manage disease. Yet, we do not believe starling control should be used as a stand alone tool to reduce S. enterica infections. Rather starling control could be used as part of a comprehensive disease management plan for concentrated animal feeding operations
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