1,337 research outputs found
Attenuation of transcriptional bursting in mRNA transport
Due to the stochastic nature of biochemical processes, the copy number of any
given type of molecule inside a living cell often exhibits large temporal
fluctuations. Here, we develop analytic methods to investigate how the noise
arising from a bursting input is reshaped by a transport reaction which is
either linear or of the Michaelis-Menten type. A slow transport rate smoothes
out fluctuations at the output end and minimizes the impact of bursting on the
downstream cellular activities. In the context of gene expression in eukaryotic
cells, our results indicate that transcriptional bursting can be substantially
attenuated by the transport of mRNA from nucleus to cytoplasm. Saturation of
the transport mediators or nuclear pores contributes further to the noise
reduction. We suggest that the mRNA transport should be taken into account in
the interpretation of relevant experimental data on transcriptional bursting.Comment: 18 pages, 3 figure
Observation of forbidden phonons and dark excitons by resonance Raman scattering in few-layer WS
The optical properties of the two-dimensional (2D) crystals are dominated by
tightly bound electron-hole pairs (excitons) and lattice vibration modes
(phonons). The exciton-phonon interaction is fundamentally important to
understand the optical properties of 2D materials and thus help develop
emerging 2D crystal based optoelectronic devices. Here, we presented the
excitonic resonant Raman scattering (RRS) spectra of few-layer WS excited
by 11 lasers lines covered all of A, B and C exciton transition energies at
different sample temperatures from 4 to 300 K. As a result, we are not only
able to probe the forbidden phonon modes unobserved in ordinary Raman
scattering, but also can determine the bright and dark state fine structures of
1s A exciton. In particular, we also observed the quantum interference between
low-energy discrete phonon and exciton continuum under resonant excitation. Our
works pave a way to understand the exciton-phonon coupling and many-body
effects in 2D materials.Comment: 14 pages, 11 figure
Investigating the topological structure of quenched lattice QCD with overlap fermions by using multi-probing approximation
The topological charge density and topological susceptibility are determined
by multi-probing approximation using overlap fermions in quenched SU(3) gauge
theory. Then we investigate the topological structure of the quenched QCD
vacuum, and compare it with results from the all-scale topological density, the
results are consistent. Random permuted topological charge density is used to
check whether these structures represent underlying ordered properties.
Pseudoscalar glueball mass is extracted from the two-point correlation function
of the topological charge density. We study ensembles of different lattice
spacing with the same lattice volume , the results are
compatible with the results of all-scale topological charge density, and the
topological structures revealed by multi-probing are much closer to all-scale
topological charge density than that by eigenmode expansion.Comment: 12 pages,34 figure
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Linezolid and Rifampicin Combination to Combat cfr-Positive Multidrug-Resistant MRSA in Murine Models of Bacteremia and Skin and Skin Structure Infection.
Linezolid resistance mediated by the cfr gene in MRSA represents a global concern. We investigated relevant phenotype differences between cfr-positive and -negative MRSA that contribute to pathogenesis, and the efficacy of linezolid-based combination therapies in murine models of bacteremia and skin and skin structure infection (SSSI). As a group, cfr-positive MRSA exhibited significantly reduced susceptibilities to the host defense peptides tPMPs, human neutrophil peptide-1 (hNP-1), and cathelicidin LL-37 (P < 0.01). In addition, increased binding to fibronectin (FN) and endothelial cells paralleled robust biofilm formation in cfr-positive vs. -negative MRSA. In vitro phenotypes of cfr-positive MRSA translated into poor outcomes of linezolid monotherapy in vivo in murine bacteremia and SSSI models. Importantly, rifampicin showed synergistic activity as a combinatorial partner with linezolid, and the EC50 of linezolid decreased 6-fold in the presence of rifampicin. Furthermore, this combination therapy displayed efficacy against cfr-positive MRSA at clinically relevant doses. Altogether, these data suggest that the use of linezolid in combination with rifampicin poses a viable therapeutic alternative for bacteremia and SSSI caused by cfr-positive multidrug resistant MRSA
How tyramine β-hydroxylase controls the production of octopamine, modulating the mobility of beetles
Biogenic amines perform many kinds of important physiological functions in the central nervous system (CNS) of insects, acting as neuromodulators, neurotransmitters, and neurohormones. The five most abundant types of biogenic amines in invertebrates are dopamine, histamine, serotonin, tyramine, and octopamine (OA). However, in beetles, an important group of model and pest insects, the role of tyramine beta-hydroxylase (T beta H) in the OA biosynthesis pathway and the regulation of behavior remains unknown so far. We therefore investigated the molecular characterization and spatiotemporal expression profiles of T beta H in red flour beetles (Triboliun castaneum). Most importantly, we detected the production of OA and measured the crawling speed of beetles after dsTcT beta H injection. We concluded that TcT beta H controls the biosynthesis amount of OA in the CNS, and this in turn modulates the mobility of the beetles. Our new results provided basic information about the key genes in the OA biosynthesis pathway of the beetles, and expanded our knowledge on the physiological functions of OA in insects
Spindle oscillations are generated in the dorsal thalamus and modulated by the thalamic reticular nucleus
Spindle waves occur during the early stage of slow wave sleep and are thought to arise in the thalamic reticular nucleus (TRN), causing inhibitory postsynaptic potential spindle-like oscillations in the dorsal thalamus that are propagated to the cortex. We have found that thalamocortical neurons exhibit membrane oscillations that have spindle frequencies, consist of excitatory postsynaptic potentials, and co-occur with electroencephalographic spindles. TRN lesioning prolonged oscillations in the medial geniculate body (MGB) and auditory cortex (AC). Injection of GABA~A~ antagonist into the MGB decreased oscillation frequency, while injection of GABA~B~ antagonist increased spindle oscillations in the MGB and cortex. Thus, spindles originate in the dorsal thalamus and TRN inhibitory inputs modulate this process, with fast inhibition facilitating the internal frequency and slow inhibition limiting spindle occurrence
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