6,098 research outputs found
Reduced Cytokine Secretions by LAK Cells of Pulmonary Tuberculosis Patients in Response to Tumor Targets In Vitro
Activation of macrophages and other immune components to release a series of proinflammatory cytokines
is one of the first events in innate resistance to intracellular infections. Severe manifestations of tuberculosis
(TB) could be caused by alterations in the balance of these cytokines. In this study, lymphokine-activated
killer (LAK) cells of TB patients and normal individuals were generated by stimulation with cytokines in vitro.
The LAK cells of both groups were further triggered with allogeneic tumor targets. Cytokines interferon-g
(IFN-g), tumor necrosis factor-a (TNF-a), and granulocyte-macrophage colony-stimulating factor (GM-CSF)
were estimated in the supernatants generated in the two groups. The aim was to see if infection with TB influenced
the secretory capacity of the immune cells in vitro. Reduced cytokine profiles were observed in TB
patients, indicating defective interactions between patient effector cells with allogeneic transformed cells compared
with normal individuals. Partial restoration of IFN-g production was seen with a combination of cytokines
interleukin-2 (IL-2) and IL-12 in TB patients. Based on the in vitro observations, we hypothesize that
in vivo also there is diminished immune cell activation of effector cells in response to the presence of infected
macrophages. This probably leads to a diminished secretory function that can be corrected by the use of such
cytokines as IL-2 and IL-12. The effector populations of TB patients are probably in a state of target-induced
anergy, allowing the bacteria to thrive, and immunomodulatory cytokines that improve the host immune response
toward countering mycobacterial infection
Connectivity percolation in suspensions of hard platelets
We present a study on connectivity percolation in suspensions of hard
platelets by means of Monte Carlo simulation. We interpret our results using a
contact-volume argument based on an effective single--particle cell model. It
is commonly assumed that the percolation threshold of anisotropic objects
scales as their inverse aspect ratio. While this rule has been shown to hold
for rod-like particles, we find that for hard plate-like particles the
percolation threshold is non-monotonic in the aspect ratio. It exhibits a
shallow minimum at intermediate aspect ratios and then saturates to a constant
value. This effect is caused by the isotropic-nematic transition pre-empting
the percolation transition. Hence the common strategy to use highly
anisotropic, conductive particles as fillers in composite materials in order to
produce conduction at low filler concentration is expected to fail for
plate-like fillers such as graphene and graphite nanoplatelets
Managing human resource management tensions in project-based organisations: evidence from Bangalore
The article analyses the methods used by a large Indian software company to manage HRM tensions with arising from its activities as a project based organisation. These measures are found to be only partially successful
Properties and occurrence rates of exoplanet candidates as a function of host star metallicity from the DR25 catalog
Correlations between the occurrence rate of exoplanets and their host star
properties provide important clues about the planet formation processes. We
studied the dependence of the observed properties of exoplanets (radius, mass,
and orbital period) as a function of their host star metallicity. We analyzed
the planetary radii and orbital periods of over 2800 candidates from
the latest data release DR25 (Q1-Q17) with revised planetary radii
based on ~DR2 as a function of host star metallicity (from the Q1-Q17
(DR25) stellar and planet catalog). With a much larger sample and improved
radius measurements, we are able to reconfirm previous results in the
literature. We show that the average metallicity of the host star increases as
the radius of the planet increases. We demonstrate this by first calculating
the average host star metallicity for different radius bins and then
supplementing these results by calculating the occurrence rate as a function of
planetary radius and host star metallicity. We find a similar trend between
host star metallicity and planet mass: the average host star metallicity
increases with increasing planet mass. This trend, however, reverses for masses
: host star metallicity drops with increasing planetary
mass. We further examined the correlation between the host star metallicity and
the orbital period of the planet. We find that for planets with orbital periods
less than 10 days, the average metallicity of the host star is higher than that
for planets with periods greater than 10 days.Comment: 14 pages, 13 Figures, Accepted for publication in The Astronomical
Journa
Ionophore-mediated transmembrane movement of divalent cations in small unilamellar liposomes: an evaluation of the chlortetracycline fluorescence technique and correlations with black lipid membrane studies
Conceptual advances in the field of membrane transport have, in the main, utilized artificial membranes, both planar and vesicular. Systems of biological interest, viz., cells and organelles, resemble vesicles in size and geometry. Methods are, therefore, required to extend the results obtained with planar membranes to liposome systems. In this report we present an analysis of a fluorescence technique, using the divalent cation probe chlortetracycline, in small, unilamellar vesicles, for the study of divalent cation fluxes. An ion carrier (X537 A) and a pore former (alamethicin) have been studied. The rate of rise of fluorescence signal and the transmembrane ion gradient have been related to transmembrane current and potential, respectively. A second power dependence of ion conduction-including the electrically silent portion thereof - on X537 A concentration, has been observed. An exponential dependence of "current" on "transmembrane potential" in the case of alamethicin is also confirmed. Possible errors in the technique are discussed
A fifteen atom silver cluster confined in bovine serum albumin
Luminescent Ag15 clusters confined in bovine serum albumin (BSA) have been prepared by a simple wet chemical route. The luminescence, exhibiting a maximum at 685 nm, is observable to the naked eye. The chemical composition of these clusters was analyzed using matrix assisted laser desorption ionization mass spectrometry (MALDI MS), X-ray photoelectron spectroscopy (XPS), and energy dispersive analysis of X-rays (EDAX). Intact Ag15@BSA is observed by MALDI MS. Multiple charge states of the cluster are observed confirming the mass assignment. The clusters showed a quantum yield of 10.71% in water and the luminescence was stable in a pH range of 1-12. Stability of the clusters was enhanced by the addition of polyvinylpyrrolidone (PVP). The clusters showed luminescence in the solid state as well. Evolution of clusters with variation in the amount of reducing agent added shows that the cluster formation goes through an intermediate state of bound silver, formed instantaneously after the addition of Ag+, which transforms to the cluster. High yield synthesis and exciting photophysical properties make our new material interesting for various applications such as biolabeling and imaging
- …