4,177 research outputs found
Polarised secretion of leukaemia inhibitory factor
Leukaemia inhibitory factor (LIF) is a cytokine that is active on a wide variety of cells. Multiple LIF transcripts have been described. The transcripts LIF-D and LIF-M encode different signal peptides, which in mouse have been associated with differential localisation of the mature protein. LIF-D is associated with a freely diffusible protein, whereas the LIF-M is associated with the extracellular matrix. The polarity of LIF secretion has yet to be described and could illuminate the mechanisms of LIF localisation. Here the polarised endogenous secretion of human LIF and IL-6 in Caco-2 cells was characterised under normal culture conditions and following induction with IL-1b. Whether the apical or basolateral membrane was stimulated influenced the pattern of secretion (LIF: Unstimulated, 59% basolateral. Dual stimulation, 68% basolateral. Basolateral stimulation, 79% basolateral. Apical stimulation, 53% basolateral). IL-6 displayed a similar dependence on the site of stimulation but was predominantly secreted at the membrane that was stimulated. To determine the effect of the alternate signal peptides on the polarity of LIF secretion, LIF was epitope tagged with FLAG. Epitope-tagging with FLAG was used to separate endogenous from exogenous protein expression. However, despite the normal biological activity of LIF-FLAG and detection of the FLAG in a western blot, detection of the LIF-FLAG under non-reducing conditions was not observed, and therefore it was unsuitable for secretion studies. Untagged LIF was expressed exogenously in Madin-Darby canine kidney (MDCK) cells under the control of a tetracycline response promoter that allowed a variety of LIF expression levels to be tested. Exogenous murine LIF was secreted predominantly from the apical (60%) membrane of MDCK cells irrespective of the signal peptide expressed
Isolation of a Novel Phage with Activity against Streptococcus mutans Biofilms
peer-reviewedStreptococcus mutans is one of the principal agents of caries formation mainly, because of its ability to form biofilms at the tooth surface. Bacteriophages (phages) are promising antimicrobial agents that could be used to prevent or treat caries formation by S. mutans. The aim of this study was to isolate new S. mutans phages and to characterize their antimicrobial properties. A new phage, ɸAPCM01, was isolated from a human saliva sample. Its genome was closely related to the only two other available S. mutans phage genomes, M102 and M102AD. ɸAPCM01 inhibited the growth of S. mutans strain DPC6143 within hours in broth and in artificial saliva at multiplicity of infections as low as 2.5x10-5. In the presence of phage ɸAPCM01 the metabolic activity of a S. mutans biofilm was reduced after 24 h of contact and did not increased again after 48 h, and the live cells in the biofilm decreased by at least 5 log cfu/ml. Despite its narrow host range, this newly isolated S. mutans phage exhibits promising antimicrobial properties
Developmental appearance of factors that bind specifically to cis-regulatory sequences of a gene expressed in the sea urchin embryo
Previous gene-transfer experiments have identified a 2500-nucleotide 5' domain of the CyIIIa cytoskeletal actin gene, which contains cis-regulatory sequences that are necessary and sufficient for spatial and temporal control of CyIIIa gene expression during embryogenesis. This gene is activated in late cleavage, exclusively in aboral ectoderm cell lineages. In this study, we focus on interactions demonstrated in vitro between sequences of the regulatory domain and proteins present in crude extracts derived from sea urchin embryo nuclei and from unfertilized eggs. Quantitative gel-shift measurements are utilized to estimate minimum numbers of factor molecules per embryo at 24 hr postfertilization, when the CyIIIa gene is active, at 7 hr, when it is still silent, and in the unfertilized egg. We also estimate the binding affinity preferences (K_r) of the various factors for their respective sites, relative to their affinity for synthetic DNA competitors. At least 14 different specific interactions occur within the regulatory regions, some of which produce multiple DNA-protein complexes. Values of K_r range from approximately 2 x 10^4 to approximately 2 x 10^6 for these factors under the conditions applied. With one exception, the minimum factor prevalences that we measured in the 400-cell 24-hr embryo nuclear extracts fell within the range of 2 x 10^5 to 2 x 10^6 molecules per embryo, i.e., a few hundred to a few thousand molecules per nucleus. Three developmental patterns were observed with respect to factor prevalence: Factors reacting at one site were found in unfertilized egg cytoplasm at about the same level per egg or embryo as in 24-hr embryo nuclei; factors reacting with five other regions of the regulatory domain are not detectable in egg cytoplasm but in 7-hr mid-cleavage-stage embryo, nuclei are already at or close to their concentrations in the 24-hr embryo nuclei; and factors reacting with five additional regions are not detectable in egg cytoplasm and are low in 7-hr embryo nuclei, i.e., ⩽10% per embryo of the level they attain in 24-hr embryo nuclei. The rise in concentration of factors of the latter class could provide the proximal cause for the temporal activation of the CyIIIa gene at the early blastula stage
Does the Debris Disk around HD 32297 Contain Cometary Grains?
We present an adaptive optics imaging detection of the HD 32297 debris disk
at L' (3.8 \microns) obtained with the LBTI/LMIRcam infrared instrument at the
LBT. The disk is detected at signal-to-noise per resolution element ~ 3-7.5
from ~ 0.3-1.1" (30-120 AU). The disk at L' is bowed, as was seen at shorter
wavelengths. This likely indicates the disk is not perfectly edge-on and
contains highly forward scattering grains. Interior to ~ 50 AU, the surface
brightness at L' rises sharply on both sides of the disk, which was also
previously seen at Ks band. This evidence together points to the disk
containing a second inner component located at 50 AU. Comparing the
color of the outer (50 /AU ) portion of the disk at L' with
archival HST/NICMOS images of the disk at 1-2 \microns allows us to test the
recently proposed cometary grains model of Donaldson et al. 2013. We find that
the model fails to match the disk's surface brightness and spectrum
simultaneously (reduced chi-square = 17.9). When we modify the density
distribution of the model disk, we obtain a better overall fit (reduced
chi-square = 2.9). The best fit to all of the data is a pure water ice model
(reduced chi-square = 1.06), but additional resolved imaging at 3.1 \microns is
necessary to constrain how much (if any) water ice exists in the disk, which
can then help refine the originally proposed cometary grains model.Comment: Accepted to ApJ January 13, 2014. 12 pages (emulateapj style), 9
figures, 1 tabl
GODMAX: Modeling gas thermodynamics and matter distribution using JAX
We introduce GODMAX (Gas thermODynamics and Matter distribution using jAX), a
novel code designed to calculate correlations between the cosmological matter
distribution and various gas thermodynamic quantities. Utilizing the extensive
ANTILLES suite of 200 hydrodynamical simulations with a diverse range of
baryonic feedback strengths, we jointly fit the 3D profiles of total matter
distribution, electron density, and electron pressure across various halo
masses and redshifts. By accommodating significant variations in gas profiles
expected due to baryonic feedback, solving exact hydrostatic equilibrium
equation and offering flexible modeling of non-thermal pressure support, GODMAX
has the capability to jointly fit all these profiles within the measurement
uncertainties. This advancement enables, for the first time, robust joint
analyses of multiple cosmic probes, including the kinetic and thermal
Sunyaev-Zel'dovich effect, weak lensing, and X-ray observations. Furthermore,
the model accurately captures correlations between the total matter power
suppression due to baryonic feedback and local average thermodynamic
quantities, such as the baryon fraction and integrated tSZ effect, in high-mass
halos, aligning with observations from hydrodynamical simulations. Looking
ahead, we forecast the expected constraints on cosmological and baryonic
parameters from upcoming weak lensing catalogs from the LSST and tSZ maps from
the Simons Observatory. This analysis underscores the importance of
cross-correlations between weak lensing and tSZ in enhancing parameter
constraints by resolving major systematic uncertainties due to baryonic
physics. The GODMAX code leverages the JAX library, resulting in a fully
differentiable halo model with native GPU compilation support.Comment: 17 pages, 9 figure
Resilience of SAR11 bacteria to rapid acidification in the high latitude open ocean
Ubiquitous SAR11 Alphaproteobacteria numerically dominate marine planktonic communities. Because they are excruciatingly difficult to cultivate, there is comparatively little known about their physiology and metabolic responses to long- and short- term environmental changes. As surface oceans take up anthropogenic, atmospheric CO2, the consequential process of ocean acidification could affect the global biogeochemical significance of SAR11. Shipping accidents or inadvertent release of chemicals from industrial plants can have strong short-term local effects on oceanic SAR11. This study investigated the effect of 2.5 fold acidification of seawater on the metabolism of SAR11 and other heterotrophic bacterioplankton along a natural temperature gradient crossing the North Atlantic Ocean, Norwegian and Greenland Seas. Uptake rates of the amino acid leucine by SAR11 cells as well as other bacterioplankton remained similar to controls despite an instant ∼50% increase in leucine bioavailability upon acidification. This high physiological resilience to acidification even without acclimation, suggests that open ocean dominant bacterioplankton are able to cope even with sudden and therefore more likely with long-term acidification effects
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