An investigation of the structure and kinematics of the spiral galaxy NGC 6503

The spiral galaxy NGC 6503 exhibits a regular kinematical structure except for a remarkable drop of the stellar velocity dispersion values in the central region. To investigate the dynamics of the disc a theoretical framework has been described. This includes a mass decomposition of the galaxy into a family of disc/halo realizations compatible with the observed photometry and rotation curve. For this family stellar velocity dispersion values and stability parameters were calculated, showing that the more massive discs, although having larger dispersions, are less stable. However, a reliable theoretical description of the inner regions where the drop occurs cannot be given. That is why we have resorted to numerical calculations. Pure stellar 3d simulations have been performed for the family of decompositions. A clear result is that disc/dark halo mass ratios approaching those of the maximum disc limit generate a large bar structure. This is incompatible with the observed morphology of NGC 6503. For the larger radii the stellar kinematics resulting from the simulations essentially agrees with that predicted by the theory, but the central velocity dispersion drop could not be reproduced. A close inspection reveals that the central nuclear region is very small and bright. Therefore, tentatively, this nucleus was considered as an isothermal sphere and a core fitting procedure was applied. For an adopted equal mass-to-light ratio of disc and nucleus, a velocity dispersion of 21.5 km/s is predicted, in excellent agreement with the observed central value. The observed dispersion drop can thus be explained by a separate kinematically distinct galactic component.Comment: 14 pages, Latex, use mn.sty style fil

Pathlengths of open channels in multiple scattering media

We report optical measurements of the spectral width of open transmission channels in a three-dimensional diffusive medium. The light transmission through a sample is enhanced by efficiently coupling to open transmission channels using repeated digital optical phase conjugation. The spectral properties are investigated by enhancing the transmission, fixing the incident wavefront and scanning the wavelength of the laser. We measure the transmitted field to extract the field correlation function and the enhancement of the total transmission. We find that optimizing the total transmission leads to a significant increase in the frequency width of the field correlation function. Additionally we find that the enhanced transmission persists over an even larger frequency bandwidth. This result shows open channels in the diffusive regime are spectrally much wider than previous measurements in the localized regime suggest

Unraveling Heterogeneity in Epithelial Cell Fates of the Mammary Gland and Breast Cancer.

Fluidity in cell fate or heterogeneity in cell identity is an interesting cell biological phenomenon, which at the same time poses a significant obstacle for cancer therapy. The mammary gland seems a relatively straightforward organ with stromal cells and basal- and luminal- epithelial cell types. In reality, the epithelial cell fates are much more complex and heterogeneous, which is the topic of this review. Part of the complexity comes from the dynamic nature of this organ: the primitive epithelial tree undergoes extensively remodeling and expansion during puberty, pregnancy, and lactation and, unlike most other organs, the bulk of mammary gland development occurs late, during puberty. An active cell biological debate has focused on lineage commitment to basal- and luminal- epithelial cell fates by epithelial progenitor and stem cells; processes that are also relevant to cancer biology. In this review, we discuss the current understanding of heterogeneity in mammary gland and recent insights obtained through lineage tracing, signaling assays, and organoid cultures. Lastly, we relate these insights to cancer and ongoing efforts to resolve heterogeneity in breast cancer with single-cell RNAseq approaches

Different evolutionary pathways underlie the morphology of wrist bones in hominoids

BACKGROUND The hominoid wrist has been a focus of numerous morphological analyses that aim to better understand long-standing questions about the evolution of human and hominoid hand use. However, these same analyses also suggest various scenarios of complex and mosaic patterns of morphological evolution within the wrist and potentially multiple instances of homoplasy that would benefit from require formal analysis within a phylogenetic context.We identify morphological features that principally characterize primate - and, in particular, hominoid (apes, including humans) - wrist evolution and reveal the rate, process and evolutionary timing of patterns of morphological change on individual branches of the primate tree of life. Linear morphological variables of five wrist bones - the scaphoid, lunate, triquetrum, capitate and hamate - are analyzed in a diverse sample of extant hominoids (12 species, 332 specimens), Old World (8 species, 43 specimens) and New World (4 species, 26 specimens) monkeys, fossil Miocene apes (8 species, 20 specimens) and Plio-Pleistocene hominins (8 species, 18 specimens). RESULT Results reveal a combination of parallel and synapomorphic morphology within haplorrhines, and especially within hominoids, across individual wrist bones. Similar morphology of some wrist bones reflects locomotor behaviour shared between clades (scaphoid, triquetrum and capitate) while others (lunate and hamate) indicate clade-specific synapomorphic morphology. Overall, hominoids show increased variation in wrist bone morphology compared with other primate clades, supporting previous analyses, and demonstrate several occurrences of parallel evolution, particularly between orangutans and hylobatids, and among hominines (extant African apes, humans and fossil hominins). CONCLUSIONS Our analyses indicate that different evolutionary processes can underlie the evolution of a single anatomical unit (the wrist) to produce diversity in functional and morphological adaptations across individual wrist bones. These results exemplify a degree of evolutionary and functional independence across different wrist bones, the potential evolvability of skeletal morphology, and help to contextualize the postcranial mosaicism observed in the hominin fossil record

A clinically relevant model of osteoinduction: a process requiring calcium phosphate and BMP/Wnt signalling

In this study, we investigated a clinically relevant model of in vivo ectopic bone formation utilizing human periosteum derived cells (HPDCs) seeded in a Collagraft carrier and explored the mechanisms by which this process is driven. Bone formation occurred after eight weeks when a minimum of one million HPDCs was loaded on Collagraft carriers and implanted subcutaneously in NMRI nu/nu mice. De novo bone matrix, mainly secreted by the HPDCs, was found juxta-proximal of the calcium phosphate (CaP) granules suggesting that CaP may have triggered the 'osteoinductive program'. Indeed, removal of the CaP granules by ethylenediaminetetraacetic acid decalcification prior to cell seeding and implantation resulted in loss of bone formation. In addition, inhibition of endogenous bone morphogenetic protein and Wnt signalling by overexpression of the secreted antagonists Noggin and Frzb, respectively, also abrogated osteoinduction. Proliferation of the engrafted HPDCs was strongly reduced in the decalcified scaffolds or when seeded with adenovirus-Noggin/Frzb transduced HPDCs indicating that cell division of the engrafted HPDCs is required for the direct bone formation cascade. These data suggest that this model of bone formation is similar to that observed during physiological intramembranous bone development and may be of importance when investigating tissue engineering strategies.Published versio