158 research outputs found
Bacterial porin disrupts mitochondrial membrane potential and sensitizes host cells to apoptosis
The bacterial PorB porin, an ATP-binding beta-barrel protein of pathogenic Neisseria gonorrhoeae, triggers host cell apoptosis by an unknown mechanism. PorB is targeted to and imported by host cell mitochondria, causing the breakdown of the mitochondrial membrane potential (delta psi m). Here, we show that PorB induces the condensation of the mitochondrial matrix and the loss of cristae structures, sensitizing cells to the induction of apoptosis via signaling pathways activated by BH3-only proteins. PorB is imported into mitochondria through the general translocase TOM but, unexpectedly, is not recognized by the SAM sorting machinery, usually required for the assembly of beta-barrel proteins in the mitochondrial outer membrane. PorB integrates into the mitochondrial inner membrane, leading to the breakdown of delta psi m. The PorB channel is regulated by nucleotides and an isogenic PorB mutant defective in ATP-binding failed to induce delta psi m loss and apoptosis, demonstrating that dissipation of delta psi m is a requirement for cell death caused by neisserial infection
Dense matter with eXTP
In this White Paper we present the potential of the Enhanced X-ray Timing and
Polarimetry (eXTP) mission for determining the nature of dense matter; neutron
star cores host an extreme density regime which cannot be replicated in a
terrestrial laboratory. The tightest statistical constraints on the dense
matter equation of state will come from pulse profile modelling of
accretion-powered pulsars, burst oscillation sources, and rotation-powered
pulsars. Additional constraints will derive from spin measurements, burst
spectra, and properties of the accretion flows in the vicinity of the neutron
star. Under development by an international Consortium led by the Institute of
High Energy Physics of the Chinese Academy of Science, the eXTP mission is
expected to be launched in the mid 2020s.Comment: Accepted for publication on Sci. China Phys. Mech. Astron. (2019
First direct measurement of Mg(,p)Al and implications for X-ray burst model-observation comparisons
Type-I X-ray burst (XRB) light curves are sensitive to the model's nuclear
input and consequently affects the model-observation comparisons.
Mg(,p)Al is among the most important reactions which
directly impact the XRB light curve. We report the first direct measurement of
Mg(,p)Al using the Active Target Time Projection Chamber.
XRB light curve model-observation comparison for the source
using new reaction rate implies a less-compact neutron star than previously
inferred. Additionally, our result removes an important uncertainty in XRB
model calculations that previously hindered extraction of the neutron star
compactness
Reaction rates and transport in neutron stars
Understanding signals from neutron stars requires knowledge about the
transport inside the star. We review the transport properties and the
underlying reaction rates of dense hadronic and quark matter in the crust and
the core of neutron stars and point out open problems and future directions.Comment: 74 pages; commissioned for the book "Physics and Astrophysics of
Neutron Stars", NewCompStar COST Action MP1304; version 3: minor changes,
references updated, overview graphic added in the introduction, improvements
in Sec IV.A.
Host Specific Diversity in Lactobacillus johnsonii as Evidenced by a Major Chromosomal Inversion and Phage Resistance Mechanisms
Genetic diversity and genomic rearrangements are a driving force in bacterial evolution and niche adaptation. We sequenced and annotated the genome of Lactobacillus johnsonii DPC6026, a strain isolated from the porcine intestinal tract. Although the genome of DPC6026 is similar in size (1.97mbp) and GC content (34.8%) to the sequenced human isolate L. johnsonii NCC 533, a large symmetrical inversion of approximately 750 kb differentiated the two strains. Comparative analysis among 12 other strains of L. johnsonii including 8 porcine, 3 human and 1 poultry isolate indicated that the genome architecture found in DPC6026 is more common within the species than that of NCC 533. Furthermore a number of unique features were annotated in DPC6026, some of which are likely to have been acquired by horizontal gene transfer (HGT) and contribute to protection against phage infection. A putative type III restriction-modification system was identified, as were novel Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) elements. Interestingly, these particular elements are not widely distributed among L. johnsonii strains. Taken together these data suggest intra-species genomic rearrangements and significant genetic diversity within the L. johnsonii species and indicate towards a host-specific divergence of L. johnsonii strains with respect to genome inversion and phage exposure
Regulation of human endometrial function: mechanisms relevant to uterine bleeding
This review focuses on the complex events that occur in the endometrium after progesterone is withdrawn (or blocked) and menstrual bleeding ensues. A detailed understanding of these local mechanisms will enhance our knowledge of disturbed endometrial/uterine function – including problems with excessively heavy menstrual bleeding, endometriosis and breakthrough bleeding with progestin only contraception. The development of novel strategies to manage these clinically significant problems depends on such new understanding as does the development of new contraceptives which avoid the endometrial side effect of breakthrough bleeding
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