106 research outputs found
Does ergometric stress test induce a procoagulative condition in patients with previous myocardial infarction
A regularly scheduled physical training program seems to have antithrombotic effects. Moreover, the hemostatic changes occurring in patients with coronary artery disease during acute exercise have not been clearly elucidated. Since stress testing is routinely performed in clinical cardiology, it would be helpful to assess whether patients with coronary artery disease are exposed to acute coronary thrombosis during or soon after sustained physical exercise. This study was designed to evaluate the effect of acute physical exercise (stress test by bicycle ergometer) on blood coagulation in a group of patients with previous myocardial infarction, and to determine whether the antithrombotic therapy commonly administered favorably influences hemostatic equilibrium. Our results suggest that exercise testing is not harmful to patients with previous myocardial infarction in regard to hemostasis and fibrinolysis and that antithrombotic therapy reduces postexercise increase in platelets
On the absolute age of the Globular Cluster M92
We present precise and deep optical photometry of the globular M92. Data were
collected in three different photometric systems: Sloan Digital Sky Survey
(g',r',i',z'; MegaCam@CFHT), Johnson-Kron-Cousins (B, V, I; various
ground-based telescopes) and Advanced Camera for Surveys (ACS) Vegamag (F475W,
F555W, F814W; Hubble Space Telescope). Special attention was given to the
photometric calibration, and the precision of the ground-based data is
generally better than 0.01 mag. We computed a new set of {\alpha}-enhanced
evolutionary models accounting for the gravitational settling of heavy elements
at fixed chemical composition ([{\alpha}/Fe]=+0.3, [Fe/H]=-2.32 dex, Y=0.248).
The isochrones -- assuming the same true distance modulus ({\mu}=14.74 mag),
the same reddening (E(B-V)=0.025+-0.010 mag), and the same reddening law --
account for the stellar distribution along the main sequence and the red giant
branch in different Color-Magnitude Diagrams (i',g'-i' ; i',g'-r' ; i',g'-z' ;
I,B-I ; F814W,F475W-F814W). The same outcome applies to the comparison between
the predicted Zero-Age-Horizontal-Branch (ZAHB) and the HB stars. We also found
a cluster age of 11 +/- 1.5 Gyr, in good agreement with previous estimates. The
error budget accounts for uncertainties in the input physics and the
photometry. To test the possible occurrence of CNO-enhanced stars, we also
computed two sets of {\alpha}- and CNO-enhanced (by a factor of three) models
both at fixed total metallicity ([M/H]=-2.10 dex) and at fixed iron abundance.
We found that the isochrones based on the former set give the same cluster age
(11 +/- 1.5 Gyr) as the canonical {\alpha}-enhanced isochrones. The isochrones
based on the latter set also give a similar cluster age (10 +/- 1.5 Gyr). These
indings support previous results concerning the weak sensitivity of cluster
isochrones to CNO-enhanced chemical mixtures.Comment: This paper makes use of data obtained from the Isaac Newton Group
Archive which is maintained as part of the CASU Astronomical Data Centre at
the Institute of Astronomy, Cambridge. This research used the facilities of
the Canadian Astronomy Data Centre operated by the National Research Council
of Canada with the support of the Canadian Space Agenc
On the Delta V_HB_bump parameter in Globular Clusters
We present new empirical estimates of the Delta V_HB_bump parameter for 15
Galactic globular clusters (GGCs) using accurate and homogeneous ground-based
optical data. Together with similar evaluations available in the literature, we
ended up with a sample of 62 GGCs covering a very broad range in metal content
(-2.16<=[M/H]<=-0.58 dex). Adopting the homogeneous metallicity scale provided
either by Kraft & Ivans (2004) or by Carretta et al. (2009), we found that the
observed Delta V_HB_bump parameters are larger than predicted. In the
metal-poor regime ([M/H]<=-1.7, -1.6 dex) 40% of GCs show discrepancies of
2sigma (~0.40 mag) or more. Evolutionary models that account either for alpha-
and CNO-enhancement or for helium enhancement do not alleviate the discrepancy
between theory and observations. The outcome is the same if we use the new
Solar heavy-element mixture. The comparison between alpha- and CNO-enhanced
evolutionary models and observations in the Carretta et al. metallicity scale
also indicates that observed Delta V_HB_bump parameters, in the metal-rich
regime ([M/H]=>0), might be systematically smaller than predicted
Regulation of the Cardiac Na+/K+ ATPase by Phospholemman
Hansraj Dhayan, Rajender Kumar, Andreas Kukol, âRegulation of the Cardiac Na+/K+ ATPase by Phospholemmanâ, in Sajal Chakraborti, Naranjan Dhalla, eds., Regulation of Membrane Na+-K+ ATPase, (Switzerland: Springer, 2016), ISBN 978-3-319-24748-9, eISBN 978-3-319-24750-2.Peer reviewe
A multi-center study on the attitudes of Malaysian emergency health care staff towards allowing family presence during resuscitation of adult patients
BACKGROUND
The practice of allowing family members to witness on-going active resuscitation has been gaining ground in many developed countries since it was first introduced in the early 1990s. In many Asian countries, the acceptability of this practice has not been well studied.
AIM
We conducted a multi-center questionnaire study to determine the attitudes of health care professionals in Malaysia towards family presence to witness ongoing medical procedures during resuscitation.
METHODS
Using a bilingual questionnaire (in Malay and English language), we asked our respondents about their attitudes towards allowing family presence (FP) as well as their actual experience of requests from families to be allowed to witness resuscitations. Multiple logistic regression was used to analyze the association between the many variables and a positive attitude towards FP.
RESULTS
Out of 300 health care professionals who received forms, 270 responded (a 90% response rate). Generally only 15.8% of our respondents agreed to allow relatives to witness resuscitations, although more than twice the number (38.5%) agreed that relatives do have a right to be around during resuscitation. Health care providers are significantly more likely to allow FP if the procedures are perceived as likely to be successful (e.g., intravenous cannulation and blood taking as compared to chest tube insertion). Doctors were more than twice as likely as paramedics to agree to FP (p-value = 0.002). This is probably due to the Malaysian work culture in our health care systems in which paramedics usually adopt a 'follow-the-leader' attitude in their daily practice.
CONCLUSION
The concept of allowing FP is not well accepted among our Malaysian health care providers
Ions modulate stress-induced nano-texture in supported fluid lipid bilayers.
Most plasma membranes comprise a large number of different molecules including lipids and proteins. In the standard fluid mosaic model, the membrane function is effected by proteins whereas lipids are largely passive and serve solely in the membrane cohesion. Here we show, using supported 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid bilayers in different saline solutions, that ions can locally induce ordering of the lipid molecules within the otherwise fluid bilayer when the latter is supported. This nanoordering exhibits a characteristic length scale of âŒ20 nm, and manifests itself clearly when mechanical stress is applied to the membrane. Atomic force microscopy (AFM) measurements in aqueous solutions containing NaCl, KCl, CaCl2, and Tris buffer show that the magnitude of the effect is strongly ion-specific, with Ca2+ and Tris, respectively, promoting and reducing stress-induced nanotexturing of the membrane. The AFM results are complemented by fluorescence recovery after photobleaching experiments, which reveal an inverse correlation between the tendency for molecular nanoordering and the diffusion coefficient within the bilayer. Control AFM experiments on other lipids and at different temperatures support the hypothesis that the nanotexturing is induced by reversible, localized gel-like solidification of the membrane. These results suggest that supported fluid phospholipid bilayers are not homogenous at the nanoscale, but specific ions are able to locally alter molecular organization and mobility, and spatially modulate the membraneâs properties on a length scale of âŒ20 nm. To illustrate this point, AFM was used to follow the adsorption of the membrane-penetrating antimicrobial peptide Temporin L in different solutions. The results confirm that the peptides do not absorb randomly, but follow the ion-induced spatial modulation of the membrane. Our results suggest that ionic effects have a significant impact for passively modulating the local properties of biological membranes, when in contact with a support such as the cytoskeleton
Detecting rotational disorder in heme proteins: A comparison between resonance Raman spectroscopy, nuclear magnetic resonance, and circular dichroism
In heme proteins, the canonical and reversed conformations result from the rotation of the heme group by 180° about the α,Îłâmeso axis in the protein pocket. The coexistence of the two different heme orientations has been observed both in proteins reconstituted with hemin and in some native proteins. The reversal of the heme orientation can also change certain functional properties of heme proteins. Complementing the results from other experimental techniques, like circular dichroism and nuclear magnetic resonance, resonance Raman spectroscopy provides detailed information on the structure of the reversed heme. This allows one to elucidate the effects of the heme rotation on the vibrational spectra of the peripheral substituents, especially the vinyl groups. Furthermore, the combination of resonance Raman spectroscopy on single crystals and solution samples of heme proteins is proposed to be a sensitive tool to detect heme orientational disorder, even in the absence of structural data
Au25(SCnH2 n+1)18 Clusters in Biomimetic Membranes: Role of Size, Charge, and Transmembrane Potential in Direct Membrane Permeation
Gold nanoclusters and nanoparticles are promising materials for applications in nanomedicine, and therefore, understanding their interaction with cell membranes is of particular importance. A series of neutral and anionic Au25(SCnH2n+1)18 monolayer protected clusters (MPCs) (briefly, Cn0 and Cn- clusters), was embedded into two types of biomimetic membranes supported by mercury electrodes. The first was a dioleoylphosphatidylcholine (DOPC) self-assembled monolayer (SAM), whereas the second was a tethered bilayer lipid membrane (tBLM) obtained by first anchoring a thiolipid monolayer to the mercury surface and then self-assembling a DOPC monolayer on top of it. The diameter of these clusters, from 1.7 to 2.7 nm depending on the thiolate ligand, is smaller than the thickness of biomembranes and biomimetic membranes. Both neutral and anionic Au25(SCnH2n+1)18 MPCs can penetrate the lipid bilayer moiety of the tBLM, without disrupting it; in particular, anionic Au25 clusters require positive transmembrane potentials to do so. Neutral Au25 clusters exchange one electron with mercury in a DOPC SAM, where they can come in contact with the mercury surface, whereas they are prevented from doing so at the tBLM because of their inability to cross the hydrophilic chain separating the lipid bilayer moiety from the mercury surface. The potential of these Au25 clusters to penetrate directly the plasma membrane is particularly convenient for targeted drug delivery. They are highly stable, biocompatible, and catalytic, and their uniform size is of importance in nanomedicine. Moreover, they may induce an efficient energy transfer to 3O2, allowing applications in radiotherapy and antimicrobial activity. \ua
Effect of a Strong Interfacial Electric Field on the Orientationof the Dipole Moment of Thiolated Aib-Oligopeptides Tetheredto Mercury on Either the N- or C-Terminus
Four oligopeptides consisting of a sequence of R-aminoisobutyric acid (Aib) residues, thiolated
at either the N- or C-terminus by means of a -(CH2)2-SH anchor, were self-assembled on mercury, which
is a substrate known to impart a high fluidity to self-assembled monolayers (SAMs). The surface dipole
potential of these peptide SAMs was estimated in 0.1 M KCl aqueous solution at a negatively charged
electrode, where the interfacial electric field is directed toward the metal. To the best of our knowledge,
this is the first estimate of the surface dipole potential of peptide SAMs in aqueous solution. The procedure
adopted consisted in measuring the charge involved in the gradual expansion of a peptide-coated mercury
drop and then combining the resulting information with an estimate of the charge density experienced by
diffuse layer ions. The dipole moment of the tethered thiolated peptides was found to be directed toward
the metal, independent of whether they were thiolated at the C- or N-terminus. This result was confirmed
by the effect of these SAMs on the kinetics and thermodynamics of the Eu(III)/Eu(II) redox couple. The
combined outcome of these studies indicates that a strong interfacial electric field orients the dipole moment
of peptide SAMs tethered to mercury, even against their \u201cnatural\u201d dipole moment
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