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International audience; Nous étudions la fonte de grosses billes de glace dans un écoulement turbulent de von Kármán à très hauts nombres de Reynolds à l'aide d'un montage optique couplant suivi de particules et ombroscopie. La mesure de la variation de taille d'une particule au cours du temps permet de mesurer le ux ther-mique à sa surface en fonction du nombre de Reynolds à l'échelle de la particule Re D. Trois situations d'écoulement sont considérées : billes librement advectées dans tout l'écoulement, billes maintenues xes dans une zone d'écoulement moyen nul, et billes maintenues xes en présence d'un écoulement moyen fort. Dans les deux cas où les billes sont xes, nous observons que le transfert thermique dans ce régime turbulent est toujours beaucoup plus fort que pour un régime laminaire, le nombre de Nusselt s'exprimant comme une loi de puissance en fonction du nombre de Reynolds : N u ∝ Re 0,8 D. Dans le cas des particules librement advectées, le transfert turbulent est encore augmenté et le nombre de Nusselt devient proportionnel au nombre de Reynolds. Le ux thermique par unité de surface est alors indé-pendant de la taille de la particule, ce qui correspond à un régime ultime de transfert de chaleur atteint lorsque la couche limite thermique est pleinement turbulente. Abstract : We study the melting dynamics of large ice balls in a turbulent von Kármán ow at very high Reynolds numbers with an optical setup based on both particles tracking and shadowgraphy. By recording the particle size variation along time, we obtain the heat ux at the ice ball surface as a function of the particle scale Reynolds number Re D. Three cases of ow are studied : ice balls freely advected in the whole ow, ice balls xed in a zero mean ow region and ice balls xed in a strong mean ow. For the two xed cases, we observe heat transfers much stronger than in laminar ows, the Nusselt number behaving as a power law as a function of the Reynolds number: N u ∝ Re 0.8 D. For freely advected ice balls, the turbulent transfert is further enhanced and the Nusselt number is proportionnal to the Reynolds number. The surface heat ux is then independant of the particles size, leading to an ultimate regime of heat transfert reached when the thermal boundary layer is fully turbulent.

International audience; We study the melting dynamics of large ice balls in a turbulent von Kármán flow at very high Reynolds number. Using an optical shadowgraphy setup, we record the time evolution of particle sizes. We study the heat transfer as a function of the particle scale Reynolds number Re D for three cases: fixed ice balls melting in a region of strong turbulence with zero mean flow, fixed ice balls melting under the action of a strong mean flow with lower fluctuations, and ice balls freely advected in the whole apparatus. For the fixed particles cases, heat transfer is observed to be much stronger than in laminar flows, the Nusselt number behaving as a power law of the Reynolds number: Nu ∝ Re 0.8 D. For freely advected ice balls, the turbulent transfer is further enhanced and the Nusselt number is proportional to the Reynolds number Nu ∝ Re D. Furthermore, the surface heat flux is found to be independent of the particles size, leading to an ultimate regime of heat transfer reached when the thermal boundary layer is fully turbulent. C 2013 AIP Publishing LLC. [http://dx.

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The Wnt/beta-catenin signaling pathway plays a key role in several cellular functions during embryonic development and adult homeostasis. The deregulation of this pathway may lead to the development of cancer, including melanoma. Deregulation of the Wnt/beta-catenin pathway occurs through either the induction/repression of, or specific mutations in, various members of this signaling pathway; this results in the stabilization of beta-catenin and its translocation from the cytoplasm to the nucleus, where it regulates transcription. Although nuclear beta-catenin is clearly involved in malignant transformation, the mechanism by which it exerts its effects remains elusive. This review focuses on the molecular and cellular mechanisms that are driven by beta-catenin and lead to melanocyte transformation. In particular, we describe how beta-catenin induces melanocyte immortalization, a novel activity of this multifunction protein. Finally, we discuss how beta-catenin-induced immortalization can cooperate with MAPKinase pathways to produce melanoma. (C) 2008 Elsevier Masson SAS. All rights reserved.

The Wnt/beta-catenin signaling pathway plays a key role in several cellular functions during embryonic development and adult homeostasis. The deregulation of this pathway may lead to the development of cancer, including melanoma. Deregulation of the Wnt/beta-catenin pathway occurs through either the induction/repression of, or specific mutations in, various members of this signaling pathway; this results in the stabilization of beta-catenin and its translocation from the cytoplasm to the nucleus, where it regulates transcription. Although nuclear beta-catenin is clearly involved in malignant transformation, the mechanism by which it exerts its effects remains elusive. This review focuses on the molecular and cellular mechanisms that are driven by beta-catenin and lead to melanocyte transformation. In particular, we describe how beta-catenin induces melanocyte immortalization, a novel activity of this multifunction protein. Finally, we discuss how beta-catenin-induced immortalization can cooperate with MAPKinase pathways to produce melanoma. (C) 2008 Elsevier Masson SAS. All rights reserved.

The Wnt/β-catenin signaling pathway plays a key role in several cellular functions during embryonic development and adult homeostasis. The deregulation of this pathway may lead to the development of cancer, including melanoma. Deregulation of the Wnt/β-catenin pathway occurs through either the induction/repression of, or specific mutations in, various members of this signaling pathway; this results in the stabilization of β-catenin and its translocation from the cytoplasm to the nucleus, where it regulates transcription. Although nuclear β-catenin is clearly involved in malignant transformation, the mechanism by which it exerts its effects remains elusive. This review focuses on the molecular and cellular mechanisms that are driven by β-catenin and lead to melanocyte transformation. In particular, we describe how β-catenin induces melanocyte immortalization, a novel activity of this multifunction protein. Finally, we discuss how β-catenin-induced immortalization can cooperate with MAPKinase pathways to produce melanoma. © 2008 Elsevier Masson SAS. All rights reserved.

A recurrent point mutation in the fibroblast growth factor receptor 3 (FGFR3) gene that converts proline 250 into arginine is commonly associated with coronal craniosynostosis and has allowed definition of a new syndrome on a molecular basis. Sixty-two patients with sporadic or familial forms of coronal craniosynostosis were investigated for the P250R FGFR3 mutation. It was identified in 20 probands originating from 27 unrelated families (74%), while only 6/35 sporadic cases (17%) harboured the mutation. In both familial and sporadic cases, females were significantly more severely affected than males. Hence, while 68% of females carrying the P250R mutation showed brachycephaly, only 35% of males had the same phenotype. In the most severe forms of the disease, the association of bicoronal craniosynostosis with hypertelorism and marked bulging of the temporal fossae were common hallmarks that might be helpful for clinical diagnosis. Taken together, these results indicate that the P250R FGFR3 mutation is mostly familial and is associated with a more severe phenotype in females than in males. The sex related severity of the condition points to the possible implication of modifier genes in this syndrome. Keywords: coronal craniosynostosis; P250R FGFR3 mutation; sex related expressivity

We report seven children from three families who had a set of common clinical features suggestive of Larsen-like syndrome, including unusual facies, bilateral dislocations of the knees and elbows, club foot, and short stature. All of the patients originated from the island of La Réunion in the Indian Ocean. The occurrence of several affected sibs in these families and the large number of consanguineous marriages on this island are consistent with autosomal recessive inheritance of the disease. Based on this hypothesis, the pedigrees were used for linkage analysis in a candidate gene assay. Lod score calculations in a pairwise study with four different fibrillar collagen genes, COL1A1, COL1A2, COL3A1, and COL5A2, allowed us to exclude these genes as the mutant loci. Supporting this, electrophoretic analysis of collagens derived from fibroblast cultures failed to show defective molecules. We conclude that this syndrome is not a collagen disorder.

Mutations in a sulfate-chloride antiporter gene, the diastrophic dysplasia sulfate transporter (DTDST), have been associated with a family of skeletal dysplasias including recessive multiple epiphyseal dysplasia, diastrophic dysplasia (DTD), atelosteogenesis type 2, and achondrogenesis type 1B (ACG1B). DTDST function is crucial for uptake of extracellular sulfate required for proteoglycan (PG) sulfation; the tissue-specific expression of the clinical phenotype may be the consequence of the high rate of PG synthesis in chondrocytes and the ensuing high sulfate requirement. We have studied the contribution of cysteine and its derivatives to PG sulfation in fibroblast and chondrocyte cultures from sulfate transporter dysplasia patients. Incubation of ACG1B fibroblasts in medium containing different concentrations of cystine indicated partial recovery of PG sulfation as measured by HPLC disaccharide analysis of chondroitin sulfate PGs; similar results were observed after incubation with N-acetylcysteine. When both compounds were tested in primary chondrocytes from a DTD patient, partial rescue of PG sulfation was observed, suggesting that the metabolic pathways producing cytoplasmic sulfate from thiols are also active in this cell type.

Hereditary multiple exostoses (HME), an autosomal skeletal disorder characterized by cartilage-capped excrescences, has been ascribed to mutations in EXT 1 and EXT 2, two tumor suppressor-related genes encoding glycosyltransferases involved in the heparan sulfate proteoglycan (HSPG) biosynthesis. Taking advantage of the availability of three different exostoses from a patient with HME harboring a premature termination codon in the EXT 1 gene, morphological, immunologic, and biochemical analyses of the samples were carried out. The cartilaginous exostosis, when compared with control cartilage, exhibited alterations in the distribution and morphology of chondrocytes with abundant bundles of actin filaments indicative of cytoskeletal defects. Chondrocytes in the exostosis were surrounded by an extracellular matrix containing abnormally high amounts of collagen type X. The unexpected presence of collagen type I unevenly distributed in the cartilage matrix further suggested that some of the hypertrophic chondrocytes detected in the cartilaginous caps of the exostoses underwent accelerated differentiation. The two mineralized exostoses presented lamellar bone arrangement undergoing intense remodeling as evidenced by the presence of numerous reversal lines. The increased electrophoretic mobility of chondroitin sulfate and dermatan sulfate proteoglycans (PGs) extracted from the two bony exostoses was ascribed to an absence of the decorin core protein. Altogether, these data indicate that EXT mutations might induce a defective endochondral ossification process in exostoses by altering actin distribution and chondrocyte differentiation and by promoting primary calcification through decorin removal.