42 research outputs found
Red cell ABO incompatibility and production of tumour necrosis factor-alpha
Tumour necrosis factor-alpha (TNF) is a major mediator of diverse pathophysiological events similar to those of haemolytic transfusion reactions (HTR), such as fever, intravascular coagulation and organ failure. However, the possible role of TNF in HTR has not been investigated. We have constructed an in vitro whole blood model of HTR to examine whether TNF may be produced in red cell ABO incompatibility. TNF was observed in plasma, in a dose dependent manner, when ABO incompatible red cells were added, but not with compatible (group O) cells. Plasma TNF levels were maximal at 2 h, and declined to control levels by 24 h. Haemolysis of incompatible red cells was accompanied by TNF production. Immune haemolysis induced TNF gene expression by buffy coat leucocytes, as determined by Northern blot analysis. Heat inactivation of plasma abolished TNF production, whereas prior treatment with interferongamma augmented the response. These results demonstrate that a major cytokine is produced in response to red cell incompatibility, and suggest that TNF may play a role in the pathogenesis of haemolytic transfusion reactions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75627/1/j.1365-2141.1991.tb04485.x.pd
Fornax 3D project: Assessing the diversity of IMF and stellar population maps within the Fornax Cluster
The stellar initial mass function (IMF) is central to our interpretation of
astronomical observables and to our understanding of most baryonic processes
within galaxies. The universality of the IMF, suggested by observations in our
own Milky Way, has been thoroughly revisited due to the apparent excess of
low-mass stars in the central regions of massive quiescent galaxies. As part of
the efforts within the Fornax 3D project, we aim to characterize the
two-dimensional IMF variations in a sample of 23 quiescent galaxies within the
Fornax cluster. For each galaxy in the sample, we measured the mean age,
metallicity, [Mg/Fe], and IMF slope maps from spatially resolved integrated
spectra. The IMF maps show a variety of behaviors and internal substructures,
roughly following metallicity variations. However, metallicity alone is not
able to fully explain the complexity exhibited by the IMF maps. In particular,
for relatively metal-poor stellar populations, the slope of the IMF seems to
depend on the (specific) star formation rate at which stars were formed.
Moreover, metallicity maps have systematically higher ellipticities than IMF
slope ones. At the same time, both metallicity and IMF slope maps have at the
same time higher ellipticities than the stellar light distribution in our
sample of galaxies. In addition we find that, regardless of the stellar mass,
every galaxy in our sample shows a positive radial [Mg/Fe] gradient. This
results in a strong [Fe/H]-[Mg/Fe] relation, similar to what is observed in
nearby, resolved galaxies. Since the formation history and chemical enrichment
of galaxies are causally driven by changes in the IMF, our findings call for a
physically motivated interpretation of stellar population measurements based on
integrated spectra that take into account any possible time evolution of the
stellar populations.Comment: 14 pages and 10 figures (plus Appendix including all the stellar
population maps). Accepted for publication in Astronomy and Astrophysic
Fornax 3D project: Automated detection of planetary nebulae in the centres of early-type galaxies and first results
Extragalactic planetary nebulae (PNe) are detectable through relatively
strong nebulous [OIII] emission and act as direct probes into the local stellar
population. Because they have an apparently universal invariant magnitude
cut-off, PNe are also considered to be a remarkable standard candle for
distance estimation. Through detecting PNe within the galaxies, we aim to
connect the relative abundances of PNe to the properties of their host galaxy
stellar population. By removing the stellar background components from FCC 167
and FCC 219, we aim to produce PN luminosity functions (PNLF) of these
galaxies, and thereby also estimate the distance modulus to these two systems.
Finally, we test the reliability and robustness of our novel detection and
analysis method. It detects unresolved point sources by their [OIII] 5007{\AA}
emission within regions that have previously been unexplored. We model the
[OIII] emissions in the spatial and spectral dimensions together, as afforded
to us by the Multi Unit Spectroscopic Explorer (MUSE), and we draw on data
gathered as part of the Fornax3D survey. For each source, we inspect the
properties of the nebular emission lines to remove other sources that might
hinder the safe construction of the PNLF, such as supernova remnants and HII
regions. As a further step, we characterise any potential limitations and draw
conclusions about the reliability of our modelling approach through a set of
simulations. By applying this novel detection and modelling approach to
integral field unit observations, we report for the distance estimates and
luminosity-specific PNe frequency values for the two galaxies. Furthermore, we
include an overview of source contamination, galaxy differences, and possible
effects on the PNe populations in the dense stellar environments.Comment: 16 pages, 17 figures, 3 tables. Accepted for publication in Astronomy
and Astrophysics Journal. Replaced with published versio