| 1. |
- Pontarollo, G., et al.
(author)
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Commensal bacteria weaken the intestinal barrier by suppressing epithelial neuropilin-1 and Hedgehog signaling
- 2023
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In: Nature Metabolism. - 2522-5812. ; 5:7, s. 1174-87
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Journal article (peer-reviewed)abstract
- The gut microbiota influences intestinal barrier integrity through mechanisms that are incompletely understood. Here we show that the commensal microbiota weakens the intestinal barrier by suppressing epithelial neuropilin-1 (NRP1) and Hedgehog (Hh) signaling. Microbial colonization of germ-free mice dampens signaling of the intestinal Hh pathway through epithelial Toll-like receptor (TLR)-2, resulting in decreased epithelial NRP1 protein levels. Following activation via TLR2/TLR6, epithelial NRP1, a positive-feedback regulator of Hh signaling, is lysosomally degraded. Conversely, elevated epithelial NRP1 levels in germ-free mice are associated with a strengthened gut barrier. Functionally, intestinal epithelial cell-specific Nrp1 deficiency (Nrp1(& UDelta;IEC)) results in decreased Hh pathway activity and a weakened gut barrier. In addition, Nrp1(& UDelta;IEC) mice have a reduced density of capillary networks in their small intestinal villus structures. Collectively, our results reveal a role for the commensal microbiota and epithelial NRP1 signaling in the regulation of intestinal barrier function through postnatal control of Hh signaling. A molecular mechanism is revealed through which commensal bacteria modulate intestinal epithelial barrier function.
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| 2. |
- Schippers, P., et al.
(author)
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Nanodust Detection between 1 and 5 AU Using Cassini Wave Measurements
- 2015
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In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 806:1
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Journal article (peer-reviewed)abstract
- The solar system contains solids of all sizes, ranging from kilometer-sized bodies to nano-sized particles. Nanograins have been detected in situ in the Earth's atmosphere, near cometary and giant planet environments, and more recently in the solar wind at 1 AU. The. latter nanograins are thought to be formed in the inner solar system dust cloud, mainly through the collisional break-up of larger grains, and are then picked up and accelerated by the magnetized solar wind because of their large charge-to-mass ratio. In the present paper, we analyze the low frequency bursty noise identified in the Cassini radio and plasma wave data during the spacecraft cruise phase inside Jupiter's orbit. The magnitude, spectral shape, and waveform of this broadband noise are. consistent with the signatures of the nano particles that traveled. at solar wind speed. and. impinged. on the spacecraft surface. Nanoparticles were observed whenever the radio instrument was turned on and able to detect them. at different heliocentric distances between Earth and Jupiter, suggesting their ubiquitous presence in the heliosphere. We analyzed the radial dependence of the nanodust flux with heliospheric distance and found that it is consistent with the dynamics of nanodust originating from the inner heliosphere and picked. up by the solar wind. The contribution of the nanodust produced in the asteroid belt appears to be negligible compared to the trapping region in the inner heliosphere. In contrast, further out, nanodust is. mainly produced by the volcanism of active moons such as Io and Enceladus.
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| 3. |
- Meyer-Vernet, Nicole, et al.
(author)
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The physics and detection of nanodust in the solar system
- 2015
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In: Plasma Physics and Controlled Fusion. - : Institute of Physics Publishing (IOPP). - 0741-3335 .- 1361-6587. ; 57:1
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Journal article (peer-reviewed)abstract
- The mass distribution of small bodies in the solar system extends over more than 35 orders of magnitude, from asteroids to nanodust, which bridge the gap between molecules and macroscopic submicron grains. The small size of nanograins compared to the relevant basic scales gives them peculiar properties. Some of these properties affect their electric charging and their large charge-to-mass ratio drives their acceleration to very high speeds in moving magnetised plasmas, as the solar wind and rotating planetary magnetospheres. The electric charge and/or high speed of nanograins have enabled them to be detected serendipitously in various parts of the solar system by several instruments designed to study larger dust, plasma particles, or waves, on a number of spacecraft. These discoveries have opened an emerging field of research, in which many open questions remain, in particular concerning the lower size limit of the particles.
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