Adiponectin (APN), a circulating adipose-derived hormone that regulates inflammation and energy metabolism, has beneficial effects on the cardiovascular disorders. Serum APN levels are lower in patients with coronary artery disease and higher in patients with chronic kidney disease. However, the precise role of APN in acute reno-vascular disease is not clear. Results of the present study show that serum APN concentration decreased after renal ischemia reperfusion (I/R) injury in mice. In addition, I/R-induced renal dysfunction (elevated serum creatinine and urea levels), inflammation (number of infiltrating neutrophils, myeloperoxidase activity), and apoptotic responses (apoptotic cell number and caspase-3 activation) were attenuated in APN-treated compared to control mice. Molecular and biochemical analysis revealed that APN up-regulates heme oxygenase-1 (HO-1) via peroxisome-proliferator-activated-receptor-α (PPARα) dependent pathway which is mediated through the enhancement of COX-2 and 6-keto PGF1α expression. Chromatin immune-precipitation assay demonstrated that APN increases the binding activity of PPARα to PPRE region of HO-1 promoter. Furthermore, APN induced HO-1 expression was only found in wild-type but not in PPARα gene deleted mice. This provides in vivo evidence that APN mediated HO-1 expression depends on PPARα regulation. In conclusion, our results provide a novel APN mediated prostacyclin-PPARα-HO-1 signaling pathway in protecting renal I/R injury.
Injectable hydrogel is one of the great interests for tissue engineering and cell encapsulation. In the study, the gelatin molecules were added to the thermosensitive chitosan/beta-glycerol phosphate (C/GP) disodium salt hydrogels to form chitosan/gelatin/beta-glycerol phosphate (C/G/GP) disodium salt hydrogels which were applied as a cell carrier for nucleus pulposus (NP) regeneration. The gelation temperature, gelation time, and gel strength of the C/G/GP hydrogels were analyzed by the rheometer. NP cells were then harvested from the intervertebral discs of the adult New Zealand white rabbits and cultured in monolayer or in C/G/GP hydrogel, respectively. The cell viability, material-mediated cytotoxicity, cell proliferation, production of sulfated glycosaminoglycans, anabolic/catabolic gene expressions, and extracellular matrix-related gene expressions of the NP cells were demonstrated. The results show that the sol/gel transition temperature of the C/G/GP hydrogel was in the range of 31.1-33.8 degrees C at neutral pH value, the gelation time was shortened, and the gel strength also improved at body temperature when compared with the C/GP hydrogel. Among those, C/GP with 1% gelatin addition showed the most promising gelation time and gel strength and were utilized in the later experiments. From the results of cell activity, cytotoxicity, and cell proliferation assays, NP cells cultured in C/G/GP hydrogel had normal cell viability and cell proliferation that indicated the hydrogel was noncytotoxicity. The amounts of sulfated glycosaminoglycans of NP cells cultured in C/G/GP hydrogels were significantly higher than monolayer cultured. Considering the extracellular matrix-related gene expression, type II collagen and aggrecan of NP cells cultured in the hydrogels greatly increased than those in monolayer culture. On the contrary, the unfavorable gene expression, such as that of type I collagen, was decreased significantly. The results reveal that gelatin added into C/GP hydrogel significantly shortened the gelation time and improved the gel strength without influencing the biocompatibility. NP cells cultured in the C/G/GP hydrogel also displayed better gene expressions when compared with the monolayer culture. This study indicates that using chitosan/gelatin hydrogel for NP cell culture is feasible and may apply in minimal invasive intervertebral disc surgery in the future.
We present wall-resolved large-eddy simulations (LES) of the incompressible Navier-Stokes equations together with empirical modeling for turbulent Taylor-Couette (TC) flow where the inner cylinder is rotating with angular velocity Ω i and the outer cylinder is stationary. With R i , R o the inner and outer radii respectively, the radius ratio is η = 0.909. The subgrid-scale (SGS) stresses are represented using the stretched-vortex subgrid-scale model while the flow is resolved close to the wall. LES is implemented in the range Re i = 10 5 − 3 × 10 6 where Re i = Ω i R i d/ν and d = R o − R i is the cylinder gap. It is shown that the LES can capture the salient features of the TC flow, including the quantitative behavior of span-wise Taylor rolls, the log-variation in the mean velocity profile and the angular momentum redistribution due to the presence of Taylor rolls. A simple empirical model of the turbulent, TC flow is developed consisting of near-wall, loglike turbulent wall layers separated by an annulus of constant angular momentum. The model is closed by a proposed scaling relation concerning the thickness of the wall layer on the inner cylinder. Model results include the Nusselt number N u (torque required to maintain the flow) and various measures of the wall-layer thickness as a function of both the Taylor number T a and η. These agree reasonably with experimental measurements, direct numerical simulation (DNS) and the present LES over a range of both T a and η.In particular, the model shows that, at fixed η < 1, N u grows like T a 1/2 divided by the square of the Lambert, (or Product-Log) function of a variable proportional to T a 1/4 . This cannot be represented by a power law dependence on T a. At the same time the wall-layer thicknesses reduce slowly in relation to the cylinder gap. This suggests an asymptotic, very large T a state consisting of constant angular momentum in the cylinder gap with u θ = 0.5 Ω i R 2 i /r, where r is the radius, with vanishingly thin turbulent wall layers at the cylinder surfaces. An extension of the model to rough-wall turbulent wall flow at the inner cylinder surface is described. This shows an asymptotic, fully rough-wall state where the torque is independent of Re i /T a, and where N u ∼ T a 1/2 . arXiv:1908.06577v1 [physics.flu-dyn]
We present wall-resolved large-eddy simulations (LES) of flow over a smooth-wall circular cylinder up to $Re_{D}=8.5\times 10^{5}$, where $Re_{D}$ is Reynolds number based on the cylinder diameter $D$ and the free-stream speed $U_{\infty }$. The stretched-vortex subgrid-scale (SGS) model is used in the entire simulation domain. For the sub-critical regime, six cases are implemented with $3.9\times 10^{3}\leqslant Re_{D}\leqslant 10^{5}$. Results are compared with experimental data for both the wall-pressure-coefficient distribution on the cylinder surface, which dominates the drag coefficient, and the skin-friction coefficient, which clearly correlates with the separation behaviour. In the super-critical regime, LES for three values of $Re_{D}$ are carried out at different resolutions. The drag-crisis phenomenon is well captured. For lower resolution, numerical discretization fluctuations are sufficient to stimulate transition, while for higher resolution, an applied boundary-layer perturbation is found to be necessary to stimulate transition. Large-eddy simulation results at $Re_{D}=8.5\times 10^{5}$, with a mesh of $8192\times 1024\times 256$, agree well with the classic experimental measurements of Achenbach (J. Fluid Mech., vol. 34, 1968, pp. 625–639) especially for the skin-friction coefficient, where a spike is produced by the laminar–turbulent transition on the top of a prior separation bubble. We document the properties of the attached-flow boundary layer on the cylinder surface as these vary with $Re_{D}$. Within the separated portion of the flow, mean-flow separation–reattachment bubbles are observed at some values of $Re_{D}$, with separation characteristics that are consistent with experimental observations. Time sequences of instantaneous surface portraits of vector skin-friction trajectory fields indicate that the unsteady counterpart of a mean-flow separation–reattachment bubble corresponds to the formation of local flow-reattachment cells, visible as coherent bundles of diverging surface streamlines.
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