Collège de France

About: Collège de France is a education organization based out in Paris, France. It is known for research contribution in the topics: Population & Receptor. The organization has 6541 authors who have published 11983 publications receiving 648742 citations. The organization is also known as: College de France.

Retinoid signaling is essential for patterning the endoderm of the third and fourth pharyngeal arches.

Abstract: The requirement of retinoic acid (RA) in the initial formation of the pharyngeal arches was investigated by treating headfold-stage mouse embryos with a pan-RAR antagonist in vitro and in vivo. This results in a complete absence of mesenchyme, arteries, nerves and epibranchial placodes of the 3rd and 4th pharyngeal arches, complete agenesis of the 3rd and 4th pouches and consistent lack of the 6th arch artery. Mesodermally derived endothelial cells are absent from the 3rd and 4th pharyngeal arch region and the distribution domain of EphA2 transcripts in mesodermal cells is shifted caudally. In situ hybridization with CRABPI, kreisler and EphA4 probes and the pattern of expression of a Wnt1-lacZ transgene show that neural crest cells (NCC) normally destined to the 3rd and 4th arches migrate ectopically. Most interestingly, the appearance of the 3rd and 4th arches is prevented by the antagonist only during a very narrow window of time, which does not correspond to the period of post-otic NCC migration. Both the timing of appearance and the nature of the defects in RAR antagonist-treated embryos indicate that migrating NCC and mesodermal cells destined to the caudal pharyngeal arches do not represent primary targets of RA action. Alterations in the endodermal expression pattern of Hoxa1, Hoxb1, Pax1, Pax9, Fgf3 and Fgf8 in response to the antagonist-induced block in RA signal transduction demonstrate for the first time that RA signaling is indispensable for the specification of the pharyngeal endoderm and suggest that this signaling is necessary to provide a permissive environment locally for the migration of NCC and mesodermal cells. Our study also indicates that the formation of the 2nd pharyngeal arch and that of the 3rd and 4th pharyngeal arches probably involve distinct RA-dependent developmental processes.

Construction of human linkage maps: Likelihood calculations for multilocus linkage analysis

Abstract: Methods are given for efficient calculation of the likelihood for multilocus linkage in families comprised of grandparents, parents, and children. Such families are being used in large-scale cooperative efforts to build a detailed linkage map of the human genome. The methods are illustrated by an application to loci on chromosome 13.

Viscosity at small scales in polymer melts

Abstract: Flows around small colloidal particles of diameter b, or in thin films, capillaries, etc., cannot always be described in terms of the macroscopic polymer viscosity. We discuss these features for entangled polymer melts, where two distinct regimes can be found: (a) the thin regime where b is smaller than the coil radius R0, but larger than the diameter of the Edwards tube; (b) the ultrathin regime, where . We consider (i) non adsorbing particles, where slippage may occur between the melt and the solid surface; (ii) “hairy” particles, which carry some bound polymer chains. We obtain scaling predictions for mobilities of spheres, of needles, and of clusters of particles. We also discuss translational and rotational diffusion of needles.