1,104 research outputs found
Biomarkers of disease progression and chemotherapeutic resistance in canine osteosarcoma
2011 Fall.Includes bibliographical references.Osteosarcoma is the most common primary bone malignancy in both humans and dogs. Over 10,000 canine patients develop this highly aggressive cancer annually and many succumb to metastatic disease in less than a year. In recent years, canine osteosarcoma has been increasingly recognized as an excellent model for the disease in humans, especially with regard to the molecular biology of the disease. Thus, research targeted at canine osteosarcoma benefits not only dogs but the field of human oncology as well. Research into the genetic and molecular derangements of osteosarcoma in both species has identified a number of oncogenes and tumor suppressor genes that may contribute to tumorigenesis. Additionally, some mediators of invasion and metastasis have been recognized (e.g. Ezrin, matrix metallopeptidases). Despite this, only a limited number of studies have been performed that examine the molecular genetics of osteosarcoma in the context of patient outcome. Thus, with the aim of identifying new target genes and pathways that contribute to disease progression and chemoresistance in osteosarcoma, we first performed transcriptomic and genomic analyses of primary tumors from dogs that had experienced good or poor outcomes following definitive treatment for osteosarcoma. These broad survey experiments yielded a selection of targets for future investigation. To further focus in on the genes that were most deranged from "normal" expression patterns, we compared gene expression patterns from tumors to those of normal bone. This study provided valuable perspective on genes that were identified in the outcome-based experiments, allowing selection of four promising gene targets to pursue. We next set out to validate in vitro models of canine osteosarcoma so that mechanistic studies could be pursued. Assays to test species and short tandem repeat identity were adapted to cell lines in use in our facility and presumed osteosarcoma cell lines were verified to be bone-derived via PCR testing of a bone-specific marker. Additionally, four anti-human antibodies were validated for use in canine samples. Two genes whose expression progressively altered with increased tumor aggressiveness where chosen for further study: insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1) and n-Myc downstream regulated gene 2 (NDRG2). IGF2BP1 has been identified as an oncofetal protein and its mRNA was strongly overexpressed in patients with the worst outcome while it was virtually undetectable in normal bone. We identified one possible mechanism for dysregulation of this gene in OSA and we also discovered that knock down of this gene in a canine osteosarcoma cell line inhibited cell invasion. NDRG2 has been dubbed a tumor suppressor in a number of different tumor types yet had not been previously investigated in osteosarcoma. We found NDRG2 mRNA to be underexpressed in all tumors relative to normal bone; patients with poor outcomes had the lowest expression levels. Multiple isoforms of the gene were found to be expressed in canine samples: these were cloned and transfected into a low-NDRG2-expressing cell line. Exogenous expression of NDRG2 in this in vitro system enhanced sensitivity to doxorubicin, one of the drugs most commonly used to treat osteosarcoma. Additionally, three possible mechanisms of dysregulation of this gene were identified. The studies presented herein progress from fact-finding surveys to in-depth functional examination of two genes that likely contribute to osteosarcoma invasion and chemoresistance. Furthermore, additional genes identified in our survey experiments offer promise for future studies into molecular mechanisms of osteosarcoma metastases and chemotherapeutic resistance. Finally, these studies have laid the groundwork for the development of gene-expression-based prognostic screens for dogs with osteosarcoma
Simultaneous X-ray/optical observations of GX 9+9 (4U 1728-16)
We report on the results of the first simultaneous X-ray (RXTE) and optical
(SAAO) observations of the luminous low mass X-ray binary (LMXB) GX 9+9 in 1999
August. The high-speed optical photometry revealed an orbital period of 4.1958
hr and confirmed previous observations, but with greater precision. No X-ray
modulation was found at the orbital period. On shorter timescales, a possible
1.4-hr variability was found in the optical light curves which might be related
to the mHz quasi-periodic oscillations seen in other LMXBs. We do not find any
significant X-ray/optical correlation in the light curves. In X-rays, the
colour-colour diagram and hardness-intensity diagram indicate that the source
shows characteristics of an atoll source in the upper banana state, with a
correlation between intensity and spectral hardness. Time-resolved X-ray
spectroscopy suggests that two-component spectral models give a reasonable fit
to the X-ray emission. Such models consist of a blackbody component which can
be interpreted as the emission from an optically thick accretion disc or an
optically thick boundary layer, and a hard Comptonized component for an
extended corona.Comment: 19 pages, 13 figures; accepted for publication in MNRA
A Serendipitous XMM-Newton Observation of the Intermediate Polar WX Pyx
We briefly describe a serendipitous observation of the little-studied
intermediate polar WX Pyx using XMM-Newton. The X-ray spin period is 1557.3
sec, confirming the optical period published in 1996. An orbital period of
approximately 5.54 hr is inferred from the separation of the spin-orbit
sidelobe components. The soft and hard band spin-folded light curves are nearly
sinusoidal in shape. The best-fit spectrum is consistent with a bremsstrahlung
temperature of about 18 keV. An upper limit of approximately 300 eV is assigned
to the presence of Fe line emission. WX Pyx lies near TX and TV Col in the
P_spin-P_orb plane.Comment: 5 pages, 5 figs; accepted A&A 2004 Dec
The polar ring galaxy AM1934-563 revisited
We report long-slit spectroscopic observations of the dust-lane polar-ring
galaxy AM1934-563 obtained with the Southern African Large Telescope (SALT)
during its performance-verification phase. The observations target the spectral
region of the Ha, [NII] and [SII] emission-lines, but show also deep NaI
stellar absorption lines that we interpret as produced by stars in the galaxy.
We derive rotation curves along the major axis of the galaxy that extend out to
about 8 kpc from the center for both the gaseous and the stellar components,
using the emission and absorption lines. We derive similar rotation curves
along the major axis of the polar ring and point out differences between these
and the ones of the main galaxy. We identify a small diffuse object visible
only in Ha emission and with a low velocity dispersion as a dwarf HII galaxy
and argue that it is probably metal-poor. Its velocity indicates that it is a
fourth member of the galaxy group in which AM1934-563 belongs. We discuss the
observations in the context of the proposal that the object is the result of a
major merger and point out some observational discrepancies from this
explanation. We argue that an alternative scenario that could better fit the
observations may be the slow accretion of cold intergalactic gas, focused by a
dense filament of galaxies in which this object is embedded (abridged).Comment: 19 pages, 13 figures, submitted to MNRAS. Some figures were bitmapped
to reduce the size. Full resolution version is available from
http://www.saao.ac.za/~akniazev/pub/AM1934_563.pd
Oocyte donation pregnancies-non-disclosure of oocyte recipient status to obstetric care providers and perinatal outcomes
Background: Oocyte donation pregnancies-non-disclosure of oocyte recipient (OR) status to obstetric care providers and perinatal outcomes. Many studies report a higher rate of pregnancy-induced hypertension (PIH) and severe pre-eclampsia (PET) in OR pregnancies. The objective is to determine the rates of non-disclosure of OR pregnancy to obstetric care providers and also the rates of perinatal complications. Method: This was a retrospective review of all oocyte recipient (OR) pregnancies, who subsequently delivered at Cork University Maternity Hospital, between 2007-2012 inclusive. Obstetric case notes were reviewed to investigate perinatal outcomes and whether OR status had been documented (unambiguously, in code or not at all). Results Less than one-third (30.2%; n=32/106) had unambiguous documentation, one-third (33%; n=35/106) had no documentation and the remainder (36.8%; n=39/106) had a code familiar only to their obstetrician. There was a high rate of gestational hypertensive disorders (28.3%; n= 30), most frequently occurring with multiple gestation. Conclusion There was a low rate of clear documentation of OR status. Gestational hypertensive disorders occurred with increased frequency
The unusual pulsation spectrum of the cool ZZ Ceti star HS 0507+0434B
We present the analysis of one week of single-site high-speed CCD photometric
observations of the cool ZZ Ceti star HS 0507+0434B. Ten independent
frequencies are detected in the star's light variations: one singlet and three
nearly-equally spaced triplets. We argue that these triplets are due to
rotationally split modes of spherical degree l=1. This is the first detection
of consistent multiplet structure in the amplitude spectrum of a cool ZZ Ceti
star and it allows us to determine the star's rotation period: 1.70 +/- 0.11 d.
We report exactly equal frequency, not period, spacings between the detected
mode groups. In addition, certain pairs of modes from the four principal groups
have frequency ratios which are very close to 3:4 or 4:5; while these ratios
are nearly exact (within one part in 10^4), they still lie outside the computed
error bars. We speculate that these relationships between different frequencies
could be caused by resonances. One of the three triplets may not be constant in
amplitude and/or frequency.
We compare our frequency solution for the combination frequencies (of which
we detected 38) to Wu's (1998, 2001) model thereof. We obtain consistent
results when trying to infer the star's convective thermal time and the
inclination angle of its rotational axis. Theoretical combination-frequency
amplitude spectra also resemble those of the observations well, and direct
theoretical predictions of the observed second-order light-curve distortions
were also reasonably successful assuming the three triplets are due to l=1
modes. Attempts to reproduce the observed combination frequencies adopting all
possible l=2 identifications for the triplets did not provide similarly
consistent results, supporting their identification with l=1.Comment: Accepted for publication in MNRAS; 12 pages, 8 figure
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