43 research outputs found
Impact of Waddlia chondrophila infection on pregnancy in the mouse.
The intracellular bacterium Waddlia chondrophila, which belongs to the Chlamydiales order, was found to be associated with miscarriage in humans. There is little to no knowledge regarding the mode of infection, impact on the neonate and pathophysiology of this emerging bacterium. We have previously shown that W. chondrophila induces a systemic infection, organ pathology and elicits T helper type 1-associated humoral immunity in a murine model of genital infection. In the present study, we took advantage of this model of infection to evaluate the impact of this bacterium on the mouse pregnancy. We used two routes of inoculation, vaginal and intrauterine, to introduce infection before and after mating. Our results show that genital infection by W. chondrophila did not have any significant impact on gestation length and maternal weight gain, nor on the number of offspring and their weight. This observation indicates that the mouse model of infection is not suitable to study the effect of W. chondrophila on pregnancy and alternative models of infection, including in vitro ones, should be used. Moreover, an indirect immunopathological mechanism activated by this bacterium should be further explored
PHARAO Laser Source Flight Model: Design and Performances
In this paper, we describe the design and the main performances of the PHARAO
laser source flight model. PHARAO is a laser cooled cesium clock specially
designed for operation in space and the laser source is one of the main
sub-systems. The flight model presented in this work is the first
remote-controlled laser system designed for spaceborne cold atom manipulation.
The main challenges arise from mechanical compatibility with space constraints,
which impose a high level of compactness, a low electric power consumption, a
wide range of operating temperature and a vacuum environment. We describe the
main functions of the laser source and give an overview of the main
technologies developed for this instrument. We present some results of the
qualification process. The characteristics of the laser source flight model,
and their impact on the clock performances, have been verified in operational
conditions.Comment: Accepted for publication in Review of Scientific Instrument
Reverse Detection of Short-Term Earthquake Precursors
We introduce a new approach to short-term earthquake prediction based on the
concept of selforganization of seismically active fault networks. That approach
is named "Reverse Detection of Precursors" (RDP), since it considers precursors
in reverse order of their appearance. This makes it possible to detect
precursors undetectable by direct analysis. Possible mechanisms underlying RDP
are outlined. RDP is described with a concrete example: we consider as
short-term precursors the newly introduced chains of earthquakes reflecting the
rise of an earthquake correlation range; and detect (retrospectively) such
chains a few months before two prominent Californian earthquakes - Landers,
1992, M = 7.6, and Hector Mine, 1999, M = 7.3, with one false alarm. Similar
results (described elsewhere) are obtained by RDP for 21 more strong
earthquakes in California (M >= 6.4), Japan (M >= 7.0) and the Eastern
Mediterranean (M >= 6.5). Validation of the RDP approach requires, as always,
prediction in advance for which this study sets up a base. We have the first
case of advance prediction; it was reported before Tokachi-oki earthquake (near
Hokkaido island, Japan), Sept. 25, 2003, M = 8.1. RDP has potentially important
applications to other precursors and to prediction of other critical phenomena
besides earthquakes. In particular, it might vindicate some short-term
precursors, previously rejected as giving too many false alarms.Comment: 17 pages, 5 figure
Social interaction, noise and antibiotic-mediated switches in the intestinal microbiota
The intestinal microbiota plays important roles in digestion and resistance
against entero-pathogens. As with other ecosystems, its species composition is
resilient against small disturbances but strong perturbations such as
antibiotics can affect the consortium dramatically. Antibiotic cessation does
not necessarily restore pre-treatment conditions and disturbed microbiota are
often susceptible to pathogen invasion. Here we propose a mathematical model to
explain how antibiotic-mediated switches in the microbiota composition can
result from simple social interactions between antibiotic-tolerant and
antibiotic-sensitive bacterial groups. We build a two-species (e.g. two
functional-groups) model and identify regions of domination by
antibiotic-sensitive or antibiotic-tolerant bacteria, as well as a region of
multistability where domination by either group is possible. Using a new
framework that we derived from statistical physics, we calculate the duration
of each microbiota composition state. This is shown to depend on the balance
between random fluctuations in the bacterial densities and the strength of
microbial interactions. The singular value decomposition of recent metagenomic
data confirms our assumption of grouping microbes as antibiotic-tolerant or
antibiotic-sensitive in response to a single antibiotic. Our methodology can be
extended to multiple bacterial groups and thus it provides an ecological
formalism to help interpret the present surge in microbiome data.Comment: 20 pages, 5 figures accepted for publication in Plos Comp Bio.
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