3,929 research outputs found
Current stage of the ATCA follow-up for SPLASH
Four ground-state OH transitions were detected in emission, absorption and
maser emission in the Southern Parkes Large-Area Survey in Hydroxyl (SPLASH).
We re-observed these OH masers with the Australia Telescope Compact Array to
obtain positions with high accuracy (~1 arcsec). According to the positions, we
categorised these OH masers into different classes, i.e. star formation,
evolved stars, supernova remnants and unknown origin. We found one interesting
OH maser source (G336.644-0.695) in the pilot region, which has been studied in
detail in Qiao et al. (2016a). In this paper, we present the current stage of
the ATCA follow-up for SPLASH and discuss the potential future researches
derived from the ATCA data.Comment: 2 pages, conference, IAU symposium 33
Synthesis of triplex-forming oligonucleotide conjugates of the anticancer drug temodal
Covalent attachment of the anticancer drugs temozolomide (Temodal) and mitozolomide to triplex-forming oligonucleotides (TFOs) is a potential way of targeting these alkylating agents to specific gene sequences to maximise site-selectivity. In this work, polypyrimidine TFO conjugates of both drugs were synthesised and targeted to duplex DNA in an attempt to effect site-specific alkylation of guanine residues. Concurrently, in an attempt to enhance the triple helix stability of TFOs at neutral pH, the thermal stabilities of triplexes formed from TFOs containing isoguanine, 2-O-benzyl- and 2-O-allyl-adenine were evaluated. A novel cleavage and deprotection procedure was developed which allowed for the solid phase synthesis of the base-sensitive TFO-drug conjugates using a recently developed silyl-linked controlled pore glass (SLCPG) support. Covalent attachment of either temozolomide or mitozolomide at the 5'-end of TFO conjugates caused no destabilisation of the triplexes studied. The synthesis of a phosphoramidite derivative of mitozolomide enabled direct incorporation of this reagent into a model sequence during DNA synthesis. After cleavage and deprotection of the TFO-drug conjugate, the 5'-end mitozolomide residue was found to have decomposed presumably as a result of ring-opening of the tetrazinone ring. The base-sensitive antibacterial and antitumour agent, metronidazole, was also successfully incorporated at the 5'-end of the oligonucleotide d(T8) using conventional methods. Two C2-substituted derivatives of 2'-deoxyadenosine containing 2-O-benzyl and 2-O-allyl groups were synthesised. Hydrogenolysis of the 2-O-benzyl analogue provided a useful route, amenable to scale-up, for the synthesis of the rare nucleoside 2'-deoxyisoguanosine (isoG). Both the 2-O-allyl and 2-O-benzyl derivatives were incorporated into TFO sequences using phosphoramidite methodology. Thermal melting experiments showed that the 2-O-allyl and 2-O-benzyl groups caused marked destabilisation of the triple helices studied, in contrast to hexose-DNA duplexes, where aralkyl substituents caused significant stabilisation of duplexes. TFOs containing isoG were synthesised by Pd(O)-catalysed deallylation of 2-0-allyl adenine residues. These sequences containing isoG, in its N3- or 02-H tautomeric form, formed triple helices which were equally as stable as those containing adenine
Quinine blocks 5-HT and 5-HT3 receptor mediated peristalsis in both guinea pig and mouse ileum tissue
Introduction. Quinine is commonly used to treat malaria; however one of the principal side effects is gastrointestinal disturbances (White, 1992). 5-HT3 receptors modulate gut peristalsis (Chetty et al., 2006), and, as quinine has been shown to act as a 5-HT3 receptor antagonist (Thompson and Lummis, 2008) it is possible that these side effects result from actions at gut 5-HT3 receptors. To address this question, we examined the ability of quinine to antagonise 5-HT and 5-HT3 mediated peristalsis in guinea pig and mouse ileum.
Methods. Ileum was excised from male guinea pigs (200-300g) and C57BL/6 mice (25-35g) following cervical dislocation. Ileum segments (3-5 cm) were mounted in 50 ml organ baths containing Tryode’s solution at 35-37 °C. Concentration-response curves were constructed for 5-HT and the selective 5-HT3 agonist 2-Me-5-HT (non-cumulative doses). Quinine was pre-applied for 10 min and inhibition measured using agonist concentrations that elicited a submaximal response.
Results. Concentration-dependent contractions produced by 5-HT (pEC50 = 5.45 ± 0.17, n = 8) and the selective 5-HT3 agonist 2-Me-5-HT (5.01 ± 0.17, n = 11) were not significantly different (Student’s t-test, t = 0.619, df = 17, p = 0.544) in guinea pig ileum. Increasing concentrations of quinine were able to antagonise the activities of both 5-HT (pIC50 = 5.03 ± 0.2, n = 6) and 2-Me-5HT (pIC50 = 4.59 ± 0.26, n = 4). At mouse ileum, 5-HT (pEC50 = 7.57 ± 0.33, n = 9) was more potent (Student’s t-test, t = 3.6, df = 12, p = 0.004) than 2-Me-5-HT (pEC50 = 5.45 ± 0.58, n = 5). Quinine antagonised both the 5-HT (pIC50 = 4.87 ± 0.31, n = 7) and 2-Me-5-HT-induced (pIC50 = 6.18 ± 1.14, n = 4) contractions.
Conclusions. These results support previous electrophysiological studies that identified quinine as an antagonist at recombinant 5-HT3 receptors with IC50 values comparable with those reported here (pIC50 = 4.87, Thompson et al., 2007). Further, we found that quinine completely blocked 5-HT induced contractions in mouse and guinea pig, raising the possibility that quinine targets other 5-HT receptors in the gut (e.g., 5-HT4 receptors) and may influence intestinal function
ALMA Observations of Circumnuclear Disks in Early Type Galaxies: 12CO(2-1) and Continuum Properties
We present results from an Atacama Large Millimeter/submillimeter Array
(ALMA) Cycle 2 program to map CO(2-1) emission in nearby early-type galaxies
(ETGs) that host circumnuclear gas disks. We obtained resolution
Band 6 observations of seven ETGs selected on the basis of dust disks in Hubble
Space Telescope images. We detect CO emission in five at high signal-to-noise
ratio with the remaining two only faintly detected. All CO emission is
coincident with the dust and is in dynamically cold rotation. Four ETGs show
evidence of rapid central rotation; these are prime candidates for
higher-resolution ALMA observations to measure the black hole masses. In this
paper we focus on the molecular gas and continuum properties. Total gas masses
and H column densities for our five CO-bright galaxies are on average
and cm over the kpc-scale
disks, and analysis suggests that these disks are stabilized against
gravitational fragmentation. The continuum emission of all seven galaxies is
dominated by a central, unresolved source, and in five we also detect a
spatially extended component. The 230 GHz nuclear continua are modeled as
power laws ranging from to within the
observed frequency band. The extended continuum profiles of the two
radio-bright (and CO-faint) galaxies are roughly aligned with their radio jet
and suggests resolved synchrotron jets. The extended continua of the CO-bright
disks are coincident with optically thick dust absorption and have spectral
slopes that are consistent with thermal dust emission.Comment: 20 pages, 10 figures; accepted for publication in Ap
Observations of Global and Local Infall in NGC 1333
We report ``infall asymmetry'' in the HCO (1--0) and (3--2) lines toward
NGC 1333, extended over , a larger extent than has been
reported be fore, for any star-forming region. The infall asymmetry extends
over a major portion of the star-forming complex, and is not limited to a
single protostar, or to a single dense core, or to a single spectral line. It
seems likely that the infall asymmetry represents inward motions, and that
these motions are physically associated with the complex. Both blue-asymmetric
and red-asymmetric lines are seen, but in both the (3--2) and (1--0) lines of
HCO the vast majority of the asymmetric lines are blue, indicating inward
motions. The (3--2) line, tracing denser gas, has the spectra with the
strongest asymmetry and these spectra are associated with the protostars IRAS
4A and 4B, which most likely indicates a warm central source is affecting the
line profiles. The (3--2) and (1--0) lines usually have the same sense of
asymmetry in common positions, but their profiles differ significantly, and the
(1--0) line appears to trace motions on much larger spatial scales than does
the (3--2) line. Line profile models fit the spectra well, but do not strongly
constrain their parameters. The mass accretion rate of the inward motions is of
order 10 M/yr, similar to the ratio of stellar mass to cluster
age.Comment: 28 pages, 11 figures, 1 colour figur
Statistics of Solar Wind Electron Breakpoint Energies Using Machine Learning Techniques
Solar wind electron velocity distributions at 1 au consist of a thermal
"core" population and two suprathermal populations: "halo" and "strahl". The
core and halo are quasi-isotropic, whereas the strahl typically travels
radially outwards along the parallel and/or anti-parallel direction with
respect to the interplanetary magnetic field. With Cluster-PEACE data, we
analyse energy and pitch angle distributions and use machine learning
techniques to provide robust classifications of these solar wind populations.
Initially, we use unsupervised algorithms to classify halo and strahl
differential energy flux distributions to allow us to calculate relative number
densities, which are of the same order as previous results. Subsequently, we
apply unsupervised algorithms to phase space density distributions over ten
years to study the variation of halo and strahl breakpoint energies with solar
wind parameters. In our statistical study, we find both halo and strahl
suprathermal breakpoint energies display a significant increase with core
temperature, with the halo exhibiting a more positive correlation than the
strahl. We conclude low energy strahl electrons are scattering into the core at
perpendicular pitch angles. This increases the number of Coulomb collisions and
extends the perpendicular core population to higher energies, resulting in a
larger difference between halo and strahl breakpoint energies at higher core
temperatures. Statistically, the locations of both suprathermal breakpoint
energies decrease with increasing solar wind speed. In the case of halo
breakpoint energy, we observe two distinct profiles above and below 500 km/s.
We relate this to the difference in origin of fast and slow solar wind.Comment: Published in Astronomy & Astrophysics, 11 pages, 10 figure
Genome sequence of a gammaherpesvirus from a common bottlenose dolphin (Tursiops truncatus)
A herpesvirus genome was sequenced directly from a biopsy specimen of a rectal lesion from a female common bottlenose dolphin. This genome sequence comprises a unique region (161,235 bp) flanked by multiple copies of a terminal repeat (4,431 bp) and contains 72 putative genes. The virus was named common bottlenose dolphin gammaherpesvirus 1
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