Tropical surface singularities

In this paper, we study tropicalisations of singular surfaces in toric threefolds. We completely classify singular tropical surfaces of maximal-dimensional type, show that they can generically have only finitely many singular points, and describe all possible locations of singular points. More precisely, we show that singular points must be either vertices, or generalized midpoints and baricenters of certain faces of singular tropical surfaces, and, in some cases, there may be additional metric restrictions to faces of singular tropical surfaces.Comment: A gap in the classification was closed. 37 pages, 29 figure

Biocompatibility and degradation of the open-pored magnesium scaffolds LAE442 and La2

Porous magnesium implants are of particular interest for application as resorbable bone substitutes, due to their mechanical strength and a Young's modulus similar to bone. The objective of the present study was to compare the biocompatibility, bone and tissue ingrowth, and the degradation behaviour of scaffolds made from the magnesium alloys LAE442 (n= 40) and Mg-La2 (n= 40)in vivo. For this purpose, cylindrical magnesium scaffolds (diameter 4 mm, length 5 mm) with defined, interconnecting pores were produced by investment casting and coated with MgF2. The scaffolds were inserted into the cancellous part of the greater trochanter ossis femoris of rabbits. After implantation periods of 6, 12, 24 and 36 weeks, the bone-scaffold compounds were evaluated usingex vivo µCT80 images, histological examinations and energy dispersive x-ray spectroscopy analysis. The La2 scaffolds showed inhomogeneous and rapid degradation, with inferior osseointegration as compared to LAE442. For the early observation times, no bone and tissue could be observed in the pores of La2. Furthermore, the excessive amount of foreign body cells and fibrous capsule formation indicates insufficient biocompatibility of the La2 scaffolds. In contrast, the LAE442 scaffolds showed slow degradation and better osseointegration. Good vascularization, a moderate cellular response, bone and osteoid-like bone matrix at all implantation periods were observed in the pores of LAE442. In summary, porous LAE442 showed promise as a degradable scaffold for bone defect repair, based on its degradation behaviour and biocompatibility. However, further studies are needed to show it would have the necessary mechanical properties required over time for weight-bearing bone defects

Aging restricts the ability of mesenchymal stem cells to promote the generation of oligodendrocytes during remyelination.

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) that leads to severe neurological deficits. Due to their immunomodulatory and neuroprotective activities and their ability to promote the generation of oligodendrocytes, mesenchymal stem cells (MSCs) are currently being developed for autologous cell therapy in MS. As aging reduces the regenerative capacity of all tissues, it is of relevance to investigate whether MSCs retain their pro-oligodendrogenic activity with increasing age. We demonstrate that MSCs derived from aged rats have a reduced capacity to induce oligodendrocyte differentiation of adult CNS stem/progenitor cells. Aging also abolished the ability of MSCs to enhance the generation of myelin-like sheaths in demyelinated cerebellar slice cultures. Finally, in a rat model for CNS demyelination, aging suppressed the capability of systemically transplanted MSCs to boost oligodendrocyte progenitor cell (OPC) differentiation during remyelination. Thus, aging restricts the ability of MSCs to support the generation of oligodendrocytes and consequently inhibits their capacity to enhance the generation of myelin-like sheaths. These findings may impact on the design of therapies using autologous MSCs in older MS patients.The authors would like to thank the following funding agencies for their support: Paracelsus Medical University PMU-FFF Long-Term Fellowship L-12/01/001-RIV (to and Stand-Alone Grant E-12/15/077-RIT (both to F.J.R.); Chilean Comisión Nacional de Investigación Científica y Tecnológica (CONICYT) FONDECYT Program Regular Grant Nº 1161787 (to F.J.R.), Regular Grant Nº 1141015 (to L.F.B.); Chilean CONICYT PCI Program Grant Nº REDES170233 (to F.J.R.), Grant Nº REDES180139 and Grant Nº REDI170037; Chilean CONICYT FONDEFIDeA Program Grant Nº ID17AM0043 (to M.E.S. and F.J.R.); European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreements N HEALTH-F2-2011-278850 (INMiND) and HEALTH-F2-2011-279288 (IDEA). The work in the Küry laboratory was supported by the German Research Foundation (DFG; KU1934/2_1, KU1934/5-1) and the Christiane and Claudia Hempel Foundation for clinical and iBrain. The work in the Franklin laboratory was supported by grants from the UK Multiple Sclerosis Society and the Adelson Medical Research Foundation, and a core support grant from the Wellcome Trust and MRC to the Wellcome-MRC Cambridge Stem Cell Institute. In addition, the present work was supported by the state of Salzburg (to L.A.). We thank Armin Schneider, Sygnis Pharma AG Heidelberg, Germany, for the MBP promoter construct. We disclose any conflict of interest