2,931 research outputs found
Probing cilia-driven flow in living embryos using femtosecond laser ablation and fast imaging
Embryonic development strictly depends on fluid dynamics. As a consequence, understanding biological fluid dynamic
is essential since it is unclear how flow affects development. For example, the specification of the left-right axis in
vertebrates depends on fluid flow where beating cilia generate a directional flow necessary for breaking the embryonic
symmetry in the so-called left-right organizer. To investigate flow dynamics in vivo proper labeling methods necessitate
approaches that are compatible with both normal biology and in vivo imaging. In this study, we describe a strategy for
labeling and analyzing microscopic fluid flows in vivo that meets this challenge. We developed an all-optical approach
based on three steps. First we used sub-cellular femtosecond laser ablation to generate fluorescent micro-debris to label
the flow. The non-linear effect used in this technique allows a high spatial confinement and a low invasiveness, thus
permitting the targeting of sub-cellular regions deep inside the embryo. Then, we used fast confocal imaging and 3Dparticle
tracking were used to image and quantify the seeded flow. This approach was used to investigate the flow
generated within zebrafish left-right organizer, a micrometer scale ciliated vesicle located deep inside the embryo and
involved in breaking left-right embryonic symmetry. We mapped the velocity field within the vesicle and surrounding a
single beating cilium, and showed that this method can address the dynamics of cilia-driven flows at multiple length
scales. We could validate the flow features as predicted from previous simulations. Such detailed descriptions of fluid
movements will be valuable in unraveling the relationships between cilia-driven flow and signal transduction. More
generally, this all-optical approach opens new opportunities for investigating microscopic flow in living tissues
Usability and acceptability of four systematic review automation software packages: A mixed method design
Selling pain to the saturated self
How can we comprehend people who pay for an experience marketed as painful? On one hand consumers spend billions of dollars every year to alleviate different kinds of pain. On the other hand, millions of individuals participate in extremely painful leisure pursuits. In trying to understand this conundrum, we ethnographically study a popular adventure challenge where participants subject themselves to electric shocks, fire and freezing water. Through sensory intensification, pain brings the body into sharp focus, allowing individuals to rediscover their corporeality. In addition, painful extraordinary experiences operate as regenerative escapes from the self. By flooding the consciousness with gnawing unpleasantness, pain provides a temporary relief from the burdens of self-awareness. Finally, when leaving marks and wounds, pain helps consumers create the story of a fulfilled life. In a context of decreased physicality, market operators play a major role in selling pain to the saturated selves of knowledge workers, who use pain as a way to simultaneously escape reflexivity and craft their life narrative
Influence of the Virus LbFV and of Wolbachia in a Host-Parasitoid Interaction
Symbionts are widespread and might have a substantial effect on the outcome of interactions between species, such as in host-parasitoid systems. Here, we studied the effects of symbionts on the outcome of host-parasitoid interactions in a four-partner system, consisting of the parasitoid wasp Leptopilina boulardi, its two hosts Drosophila melanogaster and D. simulans, the wasp virus LbFV, and the endosymbiotic bacterium Wolbachia. The virus is known to manipulate the superparasitism behavior of the parasitoid whereas some Wolbachia strains can reproductively manipulate and/or confer pathogen protection to Drosophila hosts. We used two nuclear backgrounds for both Drosophila species, infected with or cured of their respective Wolbachia strains, and offered them to L. boulardi of one nuclear background, either infected or uninfected by the virus. The main defence mechanism against parasitoids, i.e. encapsulation, and other important traits of the interaction were measured. The results showed that virus-infected parasitoids are less frequently encapsulated than uninfected ones. Further experiments showed that this viral effect involved both a direct protective effect against encapsulation and an indirect effect of superparasitism. Additionally, the Wolbachia strain wAu affected the encapsulation ability of its Drosophila host but the direction of this effect was strongly dependent on the presence/absence of LbFV. Our results confirmed the importance of heritable symbionts in the outcome of antagonistic interactions.Peer reviewe
Spinorial Characterization of Surfaces into 3-dimensional homogeneous Manifolds
We give a spinorial characterization of isometrically immersed surfaces into
3-dimensional homogeneous manifolds with 4-dimensional isometry group in terms
of the existence of a particular spinor, called generalized Killing spinor.
This generalizes results by T. Friedrich for and B. Morel for \Ss^3
and \HH^3. The main argument is the interpretation of the energy-momentum
tensor of a genralized Killing spinor as the second fondamental form up to a
tensor depending on the structure of the ambient spaceComment: 35 page
Probiotics for preventing acute otitis media in children
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: to assess the effects of probiotics to prevent the occurrence and reduce the severity of acute otitis media in children.</p
- …