1,045 research outputs found
Evolution of an expanded mannose receptor gene family
Sequences of peptides from a protein specifically immunoprecipitated by an antibody, KUL01, that recognises chicken
macrophages, identified a homologue of the mammalian mannose receptor, MRC1, which we called MRC1L-B. Inspection of
the genomic environment of the chicken gene revealed an array of five paralogous genes, MRC1L-A to MRC1L-E, located
between conserved flanking genes found either side of the single MRC1 gene in mammals. Transcripts of all five genes were
detected in RNA from a macrophage cell line and other RNAs, whose sequences allowed the precise definition of spliced
exons, confirming or correcting existing bioinformatic annotation. The confirmed gene structures were used to locate
orthologues of all five genes in the genomes of two other avian species and of the painted turtle, all with intact coding
sequences. The lizard genome had only three genes, one orthologue of MRC1L-A and two orthologues of the MRC1L-B
antigen gene resulting from a recent duplication. The Xenopus genome, like that of most mammals, had only a single
MRC1-like gene at the corresponding locus. MRC1L-A and MRC1L-B genes had similar cytoplasmic regions that may be
indicative of similar subcellular migration and functions. Cytoplasmic regions of the other three genes were very divergent,
possibly indicating the evolution of a new functional repertoire for this family of molecules, which might include novel
interactions with pathogens
Surface expression, peptide repertoire, and thermostability of chicken class I molecules correlate with peptide transporter specificity.
The chicken major histocompatibility complex (MHC) has strong genetic associations with resistance and susceptibility to certain infectious pathogens. The cell surface expression level of MHC class I molecules varies as much as 10-fold between chicken haplotypes and is inversely correlated with diversity of peptide repertoire and with resistance to Marek's disease caused by an oncogenic herpesvirus. Here we show that the average thermostability of class I molecules isolated from cells also varies, being higher for high-expressing MHC haplotypes. However, we find roughly the same amount of class I protein synthesized by high- and low-expressing MHC haplotypes, with movement to the cell surface responsible for the difference in expression. Previous data show that chicken TAP genes have high allelic polymorphism, with peptide translocation specific for each MHC haplotype. Here we use assembly assays with peptide libraries to show that high-expressing B15 class I molecules can bind a much wider variety of peptides than are found on the cell surface, with the B15 TAPs restricting the peptides available. In contrast, the translocation specificity of TAPs from the low-expressing B21 haplotype is even more permissive than the promiscuous binding shown by the dominantly expressed class I molecule. B15/B21 heterozygote cells show much greater expression of B15 class I molecules than B15/B15 homozygote cells, presumably as a result of receiving additional peptides from the B21 TAPs. Thus, chicken MHC haplotypes vary in several correlated attributes, with the most obvious candidate linking all these properties being molecular interactions within the peptide-loading complex (PLC).This work was originally supported by core funding to the Basel Institute for Immunology (which was founded and supported by F. Hoffmann-La Roche & Co. Ltd., CH-4005 Basel, Switzerland), then by core funding to the Institute for Animal Health [now re-branded the Pirbright Institute, sponsored by the Biotechnology and Biological Sciences Research Council (BBSRC) of the UK] and finally by programme grant 089305 from the Wellcome Trust to JK.This is the author accepted manuscript. The final version is available from PNAS via http://dx.doi.org/10.1073/pnas.151185911
Model-Independent Diagnostics of Highly Reddened Milky Way Star Clusters: Age Calibration
The next generation near- and mid-infrared Galactic surveys will yield a
large number of new highly obscured star clusters. Detailed characterization of
these new objects with spectroscopy is time-consuming. Diagnostic tools that
will be able to characterize clusters based only on the available photometry
will be needed to study large samples of the newly found objects. The
brightness difference between the red clump and the main-sequence turn-off
point have been used as a model-independent age calibrator for clusters with
ages from a few 10 to 10 yr in the optical. Here we apply for the
first time the method in the near-infrared. We calibrated this difference in
-band, which is likely to be available for obscured clusters, and we apply
it to a number of test clusters with photometry comparable to the one that will
be yielded by the current or near-future surveys. The new calibration yields
reliable ages over the range of ages for which the red clump is present in
clusters. The slope of the relation is smoother than that of the corresponding
-band relation, reducing the uncertainty in the age determinations with
respect to the optical ones.Comment: 5 pages, 5 eps figure, accepted for publication in Astronomy and
Astrophysic
Hot dust in normal star-forming galaxies: JHKL' photometry of the ISO Key Project sample
We present JHK and 3.8-micron photometry of 26 galaxies in the Infrared Space
Observatory (ISO) Normal Galaxy Key Project (KP) sample and of seven normal
ellipticals with the aim of investigating the origin of the 4-micron emission.
The majority of the KP galaxies, and all the ellipticals, have K-L<~1.0,
consistent with stellar photospheres plus moderate dust extinction. Ten of the
26 KP galaxies have K-L>~1.0, corresponding to a flat or rising 4-micron
continuum, consistent with significant emission from hot dust at 600-1000K. K-L
is anticorrelated with ISO flux ratio F_{6.75}/F_{15}, weakly correlated with
line ratio [OI]/[CII], but not with [CII]/FIR or IRAS ratio F_{60}/F_{100}.
Photodissociation-region models for these galaxies show that the hot dust
responsible for red K-L resides in regions of high pressure and intense
far-ultraviolet radiation field. Taken together, these results suggest that
star formation in normal star-forming galaxies can assume two basic forms: an
``active'', relatively rare, mode characterized by hot dust, suppressed
Aromatic Features in Emission (AFEs), high pressure, and intense radiation
field; and the more common ``passive'' mode that occurs under more quiescent
physical conditions, with AFEs, and without hot dust. The occurrence of these
modes appears to only weakly depend on the star-formation rate per unit area.
Passive star formation over large scales makes up the bulk of star-forming
activity locally, while the ``active'' regime may dominate at high redshifts.Comment: 11 pages, 7 figures: A&A, in press (replaced 30/09/02 for error with
macro
The infrared supernova rate in starburst galaxies
We report the results of our ongoing search for extincted supernovae (SNe) at
near-infrared wavelengths. We have monitored at 2.2 micron a sample of 46
Luminous Infrared Galaxies and detected 4 SNe. The number of detections is
still small but sufficient to provide the first estimate of supernova rate at
near-infrared wavelengths. We measure a SN rate ofv 7.6+/-3.8 SNu which is an
order of magnitude larger than observed in quiescent galaxies. On the other
hand, the observed near-infrared rate is still a factor 3-10 smaller than that
estimated from the far-infrared luminosity of the galaxies. Among various
possibilities, the most likely scenario is that dust extinction is so high
(Av>30) to obscure most SNe even in the near-IR.
The role of type Ia SNe is also discussed within this context. We derive the
type Ia SN rate as a function of the stellar mass of the galaxy and find a
sharp increase toward galaxies with higher activity of star formation. This
suggests that a significant fraction of type Ia SNe are associated with young
stellar populations.
Finally, as a by-product, we give the average K-band light curve of
core-collapse SNe based on all the existing data, and review the relation
between SN rate and far-infrared luminosity.Comment: A&A, in press, 13 page
Slogging and Stumbling Toward Social Justice in a Private Elementary School: The Complicated Case of St. Malachy
This case study examines St. Malachy, an urban Catholic elementary school primarily serving children traditionally marginalized by race, class, linguistic heritage, and disability. As a private school, St. Malachy serves the public good by recruiting and retaining such traditionally marginalized students. As empirical studies involving Catholic schools frequently juxtapose them with public schools, the author presents this examination from a different tack. Neither vilifying nor glorifying Catholic schooling, this study critically examines the pursuit of social justice in this school context. Data gathered through a 1-year study show that formal and informal leaders in St. Malachy adapted their governance, aggressively sought community resources, and focused their professional development to build the capacity to serve their increasingly pluralistic student population. The analysis confirms the deepening realization that striving toward social justice is a messy, contradictory, and complicated pursuit, and that schools in both public and private sectors are allies in this pursuit
Impact Factor: outdated artefact or stepping-stone to journal certification?
A review of Garfield's journal impact factor and its specific implementation
as the Thomson Reuters Impact Factor reveals several weaknesses in this
commonly-used indicator of journal standing. Key limitations include the
mismatch between citing and cited documents, the deceptive display of three
decimals that belies the real precision, and the absence of confidence
intervals. These are minor issues that are easily amended and should be
corrected, but more substantive improvements are needed. There are indications
that the scientific community seeks and needs better certification of journal
procedures to improve the quality of published science. Comprehensive
certification of editorial and review procedures could help ensure adequate
procedures to detect duplicate and fraudulent submissions.Comment: 25 pages, 12 figures, 6 table
Protocol and statistical analysis plan for the mega randomised registry trial comparing conservative vs. liberal oxygenation targets in adults with nonhypoxic ischaemic acute brain injuries and conditions in the intensive care unit (Mega-ROX Brains)
Background: The effect of conservative vs. liberal oxygen therapy on 90-day in-hospital mortality in adults who have nonhypoxic ischaemic encephalopathy acute brain injuries and conditions and are receiving invasive mechanical ventilation in the intensive care unit (ICU) is uncertain. Objective: The objective of this study was to summarise the protocol and statistical analysis plan for the Mega-ROX Brains trial. Design, setting, and participants: Mega-ROX Brains is an international randomised clinical trial, which will be conducted within an overarching 40,000-participant, registry-embedded clinical trial comparing conservative and liberal ICU oxygen therapy regimens. We expect to enrol between 7500 and 9500 participants with nonhypoxic ischaemic encephalopathy acute brain injuries and conditions who are receiving unplanned invasive mechanical ventilation in the ICU. Main outcome measures: The primary outcome is in-hospital all-cause mortality up to 90 d from the date of randomisation. Secondary outcomes include duration of survival, duration of mechanical ventilation, ICU length of stay, hospital length of stay, and the proportion of participants discharged home. Results and conclusions: Mega-ROX Brains will compare the effect of conservative vs. liberal oxygen therapy regimens on 90-day in-hospital mortality in adults in the ICU with acute brain injuries and conditions. The protocol and planned analyses are reported here to mitigate analysis bias. Trial Registration: Australian and New Zealand Clinical Trials Registry (ACTRN 12620000391976)
Maximal care considerations when treating patients with end-stage heart failure: ethical and procedural quandaries in management of the very sick
Deciding who should receive maximal technological treatment options and who should not represents an ethical, moral, psychological and medico-legal challenge for health care providers. Especially in patients with chronic heart failure, the ethical and medico-legal issues associated with providing maximal possible care or withholding the same are coming to the forefront. Procedures, such as cardiac transplantation, have strict criteria for adequate candidacy. These criteria for subsequent listing are based on clinical outcome data but also reflect the reality of organ shortage. Lack of compliance and non-adherence to lifestyle changes represent relative contraindications to heart transplant candidacy. Mechanical circulatory support therapy using ventricular assist devices is becoming a more prominent therapeutic option for patients with end-stage heart failure who are not candidates for transplantation, which also requires strict criteria to enable beneficial outcome for the patient. Physicians need to critically reflect that in many cases, the patient’s best interest might not always mean pursuing maximal technological options available. This article reflects on the multitude of critical issues that health care providers have to face while caring for patients with end-stage heart failure
Membrane protein stability can be compromised by detergent interactions with the extramembranous soluble domains: Detergents Destabilize Extramembranous Soluble Domains
Detergent interaction with extramembranous soluble domains (ESDs) is not commonly considered an important determinant of integral membrane protein (IMP) behavior during purification and crystallization, even though ESDs contribute to the stability of many IMPs. Here we demonstrate that some generally nondenaturing detergents critically destabilize a model ESD, the first nucleotide-binding domain (NBD1) from the human cystic fibrosis transmembrane conductance regulator (CFTR), a model IMP. Notably, the detergents show equivalent trends in their influence on the stability of isolated NBD1 and full-length CFTR. We used differential scanning calorimetry (DSC) and circular dichroism (CD) spectroscopy to monitor changes in NBD1 stability and secondary structure, respectively, during titration with a series of detergents. Their effective harshness in these assays mirrors that widely accepted for their interaction with IMPs, i.e., anionic > zwitterionic > nonionic. It is noteworthy that including lipids or nonionic detergents is shown to mitigate detergent harshness, as will limiting contact time. We infer three thermodynamic mechanisms from the observed thermal destabilization by monomer or micelle: (i) binding to the unfolded state with no change in the native structure (all detergent classes); (ii) native state binding that alters thermodynamic properties and perhaps conformation (nonionic detergents); and (iii) detergent binding that directly leads to denaturation of the native state (anionic and zwitterionic). These results demonstrate that the accepted model for the harshness of detergents applies to their interaction with an ESD. It is concluded that destabilization of extramembranous soluble domains by specific detergents will influence the stability of some IMPs during purification
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