2,248 research outputs found
A quantitative comparison of sRNA-based and protein-based gene regulation
Small, non-coding RNAs (sRNAs) play important roles as genetic regulators in
prokaryotes. sRNAs act post-transcriptionally via complementary pairing with
target mRNAs to regulate protein expression. We use a quantitative approach to
compare and contrast sRNAs with conventional transcription factors (TFs) to
better understand the advantages of each form of regulation. In particular, we
calculate the steady-state behavior, noise properties, frequency-dependent gain
(amplification), and dynamical response to large input signals of both forms of
regulation. While the mean steady-state behavior of sRNA-regulated proteins
exhibits a distinctive tunable threshold-linear behavior, our analysis shows
that transcriptional bursting leads to significantly higher intrinsic noise in
sRNA-based regulation than in TF-based regulation in a large range of
expression levels and limits the ability of sRNAs to perform quantitative
signaling. Nonetheless, we find that sRNAs are better than TFs at filtering
noise in input signals. Additionally, we find that sRNAs allow cells to respond
rapidly to large changes in input signals. These features suggest a niche for
sRNAs in allowing cells to transition quickly yet reliably between distinct
states. This functional niche is consistent with the widespread appearance of
sRNAs in stress-response and quasi-developmental networks in prokaryotes.Comment: 26 pages, 8 figures; accepted for publication in Molecular Systems
Biolog
Cerebrofaciothoracic dysplasia: four new patients with a recurrent TMCO1 pathogenic variant.
Biallelic loss of function variants in the TMCO1 gene have been previously demonstrated to result in cerebrofaciothoracic dysplasia (CFTD; MIM #213980). The phenotype of this condition includes severe intellectual disability, as well as distinctive craniofacial features, including brachycephaly, synophrys, arched eyebrows, "cupid's bow" upper lip, and microdontia. In addition, nonspecific skeletal anomalies are common, including bifid ribs, scoliosis, and spinal fusion. Only 19 molecularly confirmed patients have been previously described. Here, we present four patients with CFTD, including three brothers from a Pakistani background and an additional unrelated white Scottish patient. All share the characteristic craniofacial appearance, with severe intellectual disability and skeletal abnormalities. We further define the phenotype with comparison to the published literature, and present images to define the dysmorphic features in a previously unreported ethnic group. All of our patient series are homozygous for the same c.292_293del (p.Ser98*) TMCO1 pathogenic variant, which has been previously reported only in an isolated Amish population. Thus we provide evidence that CFTD may be more common than previously thought. The patients presented here further delineate the phenotypic spectrum of CFTD and provide evidence for a recurrent pathogenic variant in TMCO1
The X-ray luminosity of solar-mass stars in the intermediate age open cluster NGC 752
AIMS. While observational evidence shows that most of the decline in a star's
X-ray activity occurs between the age of the Hyades (~8 x 10^8 yrs) and that of
the Sun, very little is known about the evolution of stellar activity between
these ages. To gain information on the typical level of coronal activity at a
star's intermediate age, we studied the X-ray emission from stars in the 1.9
Gyr old open cluster NGC 752. METHODS. We analysed a ~140 ks Chandra
observation of NGC 752 and a ~50 ks XMM-Newton observation of the same cluster.
We detected 262 X-ray sources in the Chandra data and 145 sources in the
XMM-Newton observation. Around 90% of the catalogued cluster members within
Chandra's field-of-view are detected in the X-ray. The X-ray luminosity of all
observed cluster members (28 stars) and of 11 cluster member candidates was
derived. RESULTS. Our data indicate that, at an age of 1.9 Gyr, the typical
X-ray luminosity of the cluster members with M=0.8-1.2 Msun is Lx = 1.3 x 10^28
erg s^-1, so approximately a factor of 6 less intense than that observed in the
younger Hyades. Given that Lx is proportional to the square of a star's
rotational rate, the median Lx of NGC 752 is consistent, for t > 1 Gyr, to a
decaying rate in rotational velocities v_rot ~ t^-alpha with alpha ~ 0.75,
steeper than the Skumanich relation (alpha ~ 0.5) and significantly steeper
than observed between the Pleiades and the Hyades (where alpha < 0.3),
suggesting that a change in the rotational regimes of the stellar interiors is
taking place at t ~ 1 Gyr.Comment: Accepted for publication in A&A (13 pages, 8 figures
Guaranteed clustering and biclustering via semidefinite programming
Identifying clusters of similar objects in data plays a significant role in a
wide range of applications. As a model problem for clustering, we consider the
densest k-disjoint-clique problem, whose goal is to identify the collection of
k disjoint cliques of a given weighted complete graph maximizing the sum of the
densities of the complete subgraphs induced by these cliques. In this paper, we
establish conditions ensuring exact recovery of the densest k cliques of a
given graph from the optimal solution of a particular semidefinite program. In
particular, the semidefinite relaxation is exact for input graphs corresponding
to data consisting of k large, distinct clusters and a smaller number of
outliers. This approach also yields a semidefinite relaxation for the
biclustering problem with similar recovery guarantees. Given a set of objects
and a set of features exhibited by these objects, biclustering seeks to
simultaneously group the objects and features according to their expression
levels. This problem may be posed as partitioning the nodes of a weighted
bipartite complete graph such that the sum of the densities of the resulting
bipartite complete subgraphs is maximized. As in our analysis of the densest
k-disjoint-clique problem, we show that the correct partition of the objects
and features can be recovered from the optimal solution of a semidefinite
program in the case that the given data consists of several disjoint sets of
objects exhibiting similar features. Empirical evidence from numerical
experiments supporting these theoretical guarantees is also provided
Dimensionality and dynamics in the behavior of C. elegans
A major challenge in analyzing animal behavior is to discover some underlying
simplicity in complex motor actions. Here we show that the space of shapes
adopted by the nematode C. elegans is surprisingly low dimensional, with just
four dimensions accounting for 95% of the shape variance, and we partially
reconstruct "equations of motion" for the dynamics in this space. These
dynamics have multiple attractors, and we find that the worm visits these in a
rapid and almost completely deterministic response to weak thermal stimuli.
Stimulus-dependent correlations among the different modes suggest that one can
generate more reliable behaviors by synchronizing stimuli to the state of the
worm in shape space. We confirm this prediction, effectively "steering" the
worm in real time.Comment: 9 pages, 6 figures, minor correction
Adiponectin Reduces Plasma Triglyceride by Increasing VLDL Triglyceride Catabolism
OBJECTIVE—Adiponectin is an adipocyte-derived hormone that plays an important role in glucose and lipid metabolism. The main aims of this study are to investigate the effects of adiponectin on VLDL triglyceride (VLDL-TG) metabolism and the underlying mechanism
SCN8A encephalopathy: Research progress and prospects
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/133635/1/epi13422.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/133635/2/epi13422_am.pd
Genetic and Transmission Analysis of Helicobacter pylori Strains within a Family1
Point mutations, intragenic recombination, and introduction of foreign alleles enhanced strain diversity within the family
Gas-phase and particulate products from the atmospheric degradation of an isoxazole fungicide
[EN] The isoxazole structure is present in several pesticides. However, there is a lack of information about its
degradation products after the release to the atmosphere. The main atmospheric reactions of hymexazol
(5-methylisoxazol-3-ol), selected as representative model, were investigated at a large outdoor simulation
chamber. The predominant products of atmospheric degradations were gaseous nitrogen derivates
(nitric acid, nitrogen dioxide, nitrogen oxide, nitrous acid, and peroxyacetylnitrate), ozone, and small
oxygenated compounds (formic acid, formaldehyde, and methylglyoxal). The aerosol yields were lower
than 5%, and an OH rate-dependence was observed in the nucleation, particle growth, and size distribution.
Also, the chemical composition of minor multi-oxygenated products was studied for OH-photooxidations.
More than 20 products were detected in the gas or particulate phase. The most abundant
were heterocyclic cleavage products with C4-chain and oxygenated moieties at positions 1 and 3, such
as 3,4-dioxobutanoic acid, 3-oxobutanoic acid, and 3-oxobutanal. The suggested reaction pathway is
the opening of heterocycle ring by the cleavage of N O bond and C N bond, releasing nitrogen oxides.The authors wish to thank the EUPHORE staff and J.T.B. The authors wish to acknowledge Ministerio de Ciencia y Tecnologia for IMPESTAT (CGL2010-18474/CLI) and the European Community's Seventh Framework Program under the Grant agreement no. 228335 (Eurochamp2). The Fundacion CEAM is partly supported by Generalitat Valenciana, and the projects GRACCIE (Consolider-Ingenio 2010) and FEEDBACKS (Prometeo - Generalitat Valenciana). EUPHORE instrumentation is partly funded by the Spanish Ministry of Science and Innovation, through INNPLANTA Project: PCT-440000-2010-003.Tortajada-Genaro, LA.; Borrás García, EM.; Muñoz, A. (2013). Gas-phase and particulate products from the atmospheric degradation of an isoxazole fungicide. Chemosphere. 92(8):1035-1041. https://doi.org/10.1016/j.chemosphere.2013.03.041S1035104192
Driving chronicity in rheumatoid arthritis: perpetuating role of myeloid cells
Acute inflammation is a complex and tightly regulated homeostatic process that includes leukocyte migration from the vasculature into tissues to eliminate the pathogen/injury, followed by a pro-resolving response promoting tissue repair. However, if inflammation is uncontrolled as in chronic diseases such as Rheumatoid Arthritis (RA) it leads to tissue damage and disability. Synovial tissue inflammation in RA patients is maintained by sustained activation of multiple inflammatory positive-feedback regulatory pathways in a variety of cells including myeloid cells. In this review, we will highlight recent evidence uncovering biological mechanisms contributing to the aberrant activation of myeloid cells that contributes to perpetuation of inflammation in RA, and discuss emerging data on anti-inflammatory mediators contributing to sustained remission that may inform a novel category of therapeutic targets
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