Effective mechanical properties of hexagonal boron nitride nanosheets.

We propose an analytical formulation to extract from energy equivalence principles the equivalent thickness and in-plane mechanical properties (tensile and shear rigidity, and Poisson's ratio) of hexagonal boron nitride (h-BN) nanosheets. The model developed provides not only very good agreement with existing data available in the open literature from experimental, density functional theory (DFT) and molecular dynamics (MD) simulations, but also highlights the specific deformation mechanisms existing in boron nitride sheets, and their difference with carbon-based graphitic systems.

Increased adipogenic conversion of muscle satellite cells in obese Zucker rats.

AIMS/HYPOTHESIS: Visceral and intermuscular adipose tissue (IMAT) depots account for most obesity-related metabolic and cardiovascular complications. Muscle satellite cells (SCs) are mesenchymal stem cells giving rise to myotubes and also to adipocytes, suggesting their possible contribution to IMAT origin and expansion. We investigated the myogenic differentiation of SCs and the adipogenic potential of both preadipocytes and SCs from genetically obese Zucker rats (fa/fa), focusing on the role of Wnt signaling in these differentiation processes. METHODS: SCs were isolated by single-fiber technique from flexor digitorum brevis muscle and preadipocytes were extracted from subcutaneous adipose tissue (AT). Morphological features and gene expression profile were evaluated during in vitro myogenesis and adipogenesis. Wingless-type MMTV integration site family member 10b (Wnt10b) expression was quantified by quantitative PCR in skeletal muscle and AT. RESULTS: We did not observe any difference in the proliferation rate and in the myogenic differentiation of SCs from obese and lean rats. However, a decreased insulin-induced glucose uptake was present in myotubes originating from fa/fa rats. Under adipogenic conditions, preadipocytes and SCs of obese animals displayed an enhanced adipogenesis. Wnt10b expression was reduced in obese rats in both muscle and AT. CONCLUSIONS/INTERPRETATION: Our data suggest that the increase in different fat depots including IMAT and the reduced muscle insulin sensitivity, the major phenotypical alteration of obese Zucker rats, could be ascribed to an intrinsic defect, either genetically determined or acquired, still present in both muscle and fat precursors. The involvement of Wnt10b as a regulator of both adipogenesis and muscle-to-fat conversion is suggested.

Enhancement of viability of muscle precursor cells on 3D scaffold in a perfusion bioreactor.

The aim of this study was to develop a methodology for the in vitro expansion of skeletal-muscle precursor cells (SMPC) in a three-dimensional (3D) environment in order to fabricate a cellularized artificial graft characterized by high density of viable cells and uniform cell distribution over the entire 3D domain. Cell seeding and culture within 3D porous scaffolds by conventional static techniques can lead to a uniform cell distribution only on the scaffold surface, whereas dynamic culture systems have the potential of allowing a uniform growth of SMPCs within the entire scaffold structure. In this work, we designed and developed a perfusion bioreactor able to ensure long-term culture conditions and uniform flow of medium through 3D collagen sponges. A mathematical model to assist the design of the experimental setup and of the operative conditions was developed. The effects of dynamic vs static culture in terms of cell viability and spatial distribution within 3D collagen scaffolds were evaluated at 1, 4 and 7 days and for different flow rates of 1, 2, 3.5 and 4.5 ml/min using C2C12 muscle cell line and SMPCs derived from satellite cells. C2C12 cells, after 7 days of culture in our bioreactor, perfused applying a 3.5 ml/min flow rate, showed a higher viability resulting in a three-fold increase when compared with the same parameter evaluated for cultures kept under static conditions. In addition, dynamic culture resulted in a more uniform 3D cell distribution. The 3.5 ml/min flow rate in the bioreactor was also applied to satellite cell-derived SMPCs cultured on 3D collagen scaffolds. The dynamic culture conditions improved cell viability leading to higher cell density and uniform distribution throughout the entire 3D collagen sponge for both C2C12 and satellite cells.

Rosiglitazone modifies the adipogenic potential of human muscle satellite cells.

AIMS/HYPOTHESIS: Satellite cells are responsible for postnatal skeletal muscle regeneration. It has been demonstrated that mouse satellite cells behave as multipotent stem cells. We studied the differentiation capacities of human satellite cells and evaluated the effect of the insulin sensitiser rosiglitazone, a well known peroxisome proliferative activated receptor gamma (PPARG) agonist, on their adipogenic conversion. SUBJECTS, MATERIALS AND METHODS: We obtained human satellite cells from human muscle biopsies of healthy subjects by single-fibre isolation and cultured them under myogenic, osteogenic and adipogenic conditions. Moreover, we compared the morphological features and the adipose-specific gene expression profiling, as assessed by quantitative PCR, between adipocytes differentiated from human satellite cells and those obtained from the stromal vascular fraction of human visceral fat. RESULTS: We proved by morphological analysis, mRNA expression and immunohistochemistry that human satellite cells are able to differentiate into myotubes, adipocytes and osteocytes. The addition of rosiglitazone to the adipogenic medium strongly activated PPARG expression and enhanced adipogenesis in human satellite cells, but did not in itself trigger the complete adipogenic programme. Moreover, we observed a decrease in wingless-type MMTV integration site family member 10B and an upregulation of growth differentiation factor 8 expression, both being independent of PPARG activation. CONCLUSIONS/INTERPRETATION: Human satellite cells possess a clear adipogenic potential that could explain the presence of mature adipocytes within skeletal muscle in pathological conditions such as obesity, type 2 diabetes and ageing-related sarcopenia. Rosiglitazone treatment, while enhancing adipogenesis, induces a more favourable pattern of adipocytokine expression in satellite-derived fat cells. This could partially counteract the worsening effect of intermuscular adipose tissue depots on muscle insulin sensitivity.

[The utilization of the ICNP Beta version taxonomy system for the nursing protocols' construction]. / Un'esperienza applicativa del sistema tassonomico ICNP nella costruzione di protocolli infermieristici.

The ICNP Beta version system has been used for the revision of hospital protocols on the nursing management of the central venous catheters. Despite the taxonomy defects of clarity and functionality, our experience has shown an increase of understanding and accord between builders professionals and protocol's users. Besides all. It has also been important to sensitize the participants to the experimentation of an encoded international language.