Celastrol attenuates renal injury in diabetic rats via MAPK/NF-κB pathway.

The purpose of this study was to investigate the renal protective effect of celastrol on diabetic rats. Furthermore, the mechanism of its action was discussed whether it was related to MAPK/NF-κB signaling pathway. There were a total of 36 rats. Six rats were randomly chosen as the control group. The remaining 30 rats were given 1% streptozotocin intraperitoneal injection (50 mg/kg) and were randomly divided into five groups: the model control group, the low-dose celastrol group, the high-dose celastrol group, the Tripterygium wilfordii polyglycosides group, and the MAPK/NF-κB inhibitor group. After 4 weeks of continuous administration, 24-hr urine volume, urinary protein, blood urea nitrogen, and serum creatinine content were observed, and hematoxylin-eosin (HE) staining of the kidney and liver were evaluated. p38MAPK was designated by immunohistochemical method, and NF-κB p65 in renal tissue was detected by western blotting. Our results showed that celastrol could not only reduce contents of creatinine and urea nitrogen in blood but also reduce excretion of urinary protein in diabetic rats, improve renal pathological injury, and down-regulate the expression of p38MAPK and NF-κB p65. In conclusion, celastrol could protect kidney of diabetic rats by regulating the signal pathway of MAPK/NF-κB, inhibiting inflammation and delaying renal injury.

Design, analysis and testing of a parallel-kinematic high-bandwidth XY nanopositioning stage.

This paper presents the design, analysis, and testing of a parallel-kinematic high-bandwidth XY nanopositioning stage driven by piezoelectric stack actuators. The stage is designed with two kinematic chains. In each kinematic chain, the end-effector of the stage is connected to the base by two symmetrically distributed flexure modules, respectively. Each flexure module comprises a fixed-fixed beam and a parallelogram flexure serving as two orthogonal prismatic joints. With the purpose to achieve high resonance frequencies of the stage, a novel center-thickened beam which has large stiffness is proposed to act as the fixed-fixed beam. The center-thickened beam also contributes to reducing cross-coupling and restricting parasitic motion. To decouple the motion in two axes totally, a symmetric configuration is adopted for the parallelogram flexures. Based on the analytical models established in static and dynamic analysis, the dimensions of the stage are optimized in order to maximize the first resonance frequency. Then finite element analysis is utilized to validate the design and a prototype of the stage is fabricated for performance tests. According to the results of static and dynamic tests, the resonance frequencies of the developed stage are over 13.6 kHz and the workspace is 11.2 µm × 11.6 µm with the cross-coupling between two axes less than 0.52%. It is clearly demonstrated that the developed stage has high resonance frequencies, a relatively large travel range, and nearly decoupled performance between two axes. For high-speed tracking performance tests, an inversion-based feedforward controller is implemented for the stage to compensate for the positioning errors caused by mechanical vibration. The experimental results show that good tracking performance at high speed is achieved, which validates the effectiveness of the developed stage.

Real-time inverse hysteresis compensation of piezoelectric actuators with a modified Prandtl-Ishlinskii model.

This paper presents a novel real-time inverse hysteresis compensation method for piezoelectric actuators exhibiting asymmetric hysteresis effect. The proposed method directly utilizes a modified Prandtl-Ishlinskii hysteresis model to characterize the inverse hysteresis effect of piezoelectric actuators. The hysteresis model is then cascaded in the feedforward path for hysteresis cancellation. It avoids the complex and difficult mathematical procedure for constructing an inversion of the hysteresis model. For the purpose of validation, an experimental platform is established. To identify the model parameters, an adaptive particle swarm optimization algorithm is adopted. Based on the identified model parameters, a real-time feedforward controller is implemented for fast hysteresis compensation. Finally, tests are conducted with various kinds of trajectories. The experimental results show that the tracking errors caused by the hysteresis effect are reduced by about 90%, which clearly demonstrates the effectiveness of the proposed inverse compensation method with the modified Prandtl-Ishlinskii model.

A strategy for fabrication of a three-dimensional tissue construct containing uniformly distributed embryoid body-derived cells as a cardiac patch.

Growing three-dimensional (3D) scaffolds that contain more than a few layers of seeded cells in vitro is crucial for the creation of thick and viable cardiac tissues in vivo. Embryonic stem cells (ESCs) have been used as an alternative cell source for cardiac repair; however, dissociated ESCs show poor viability in the scaffold and do not form the embryoid body (EB)-like structures. In this study, a strategy intended for cultivating EB-derived cells (EBDCs) uniformly in a porous 3D tissue scaffold was developed. This strategy employed techniques of formation of spherically symmetric EBs in a thermo-responsive hydrogel system, production of cell sheets of EBDCs in a similar hydrogel system coated with collagen and fabrication of sliced porous tissue scaffolds. The prepared EBs were collected and plated evenly in the cell-sheet culture system. After 8 days in culture, a continuous sheet of EBDCs with cell beating was obtained; our qPCR and flow cytometric analyses showed that the collagen-coated on the cell-sheet culture system can significantly enhance the population of cardiac-lineage cells. The produced EBDC sheets were then sandwiched into the sliced porous tissue scaffold. After reculture, the seeded EBDCs were redistributed uniformly throughout the scaffold, with a significant increase in mechanical strength. Cardiac-specific myosin heavy chain and alpha-actinin were expressed for some cells grown in the scaffold, while connexin 43 was clearly expressed at the cell borders. Additional studies such as employing purification techniques to enrich the population of cardiomyocytes are needed to further improve the developed tissue constructs as a bioengineered cardiac patch.

Effects of incorporation of poly(gamma-glutamic acid) in chitosan/DNA complex nanoparticles on cellular uptake and transfection efficiency.

Chitosan (CS)/DNA complex nanoparticles (NPs) have been considered as a vector for gene delivery. Although advantageous for DNA packing and protection, CS-based complexes may lead to difficulties in DNA release once arriving at the site of action. In this study, an approach through modifying their internal structure by incorporating a negatively charged poly(gamma-glutamic acid) (gamma-PGA) in CS/DNA complexes (CS/DNA/gamma-PGA NPs) is reported. The analysis of small angle X-ray scattering results revealed that DNA and gamma-PGA formed complexes with CS separately to yield two types of domains, leading to the formation of "compounded NPs". With this internal structure, the compounded NPs might disintegrate into a number of even smaller sub-particles after cellular internalization, thus improving the dissociation capacity of CS and DNA. Consequently, after incorporating gamma-PGA in CS/DNA complexes, a significant increase in their transfection efficiency was found. Interestingly, in addition to improving the release of DNA intracellularly, the incorporation of gamma-PGA in CS/DNA complexes significantly enhanced their cellular uptake. We further demonstrated that besides a non-specific charged-mediated binding to cell membranes, there were specific trypsin-cleavable proteins involved in the internalization of CS/DNA/gamma-PGA NPs. The aforementioned results indicated that gamma-PGA played multiple important roles in enhancing the cellular uptake and transfection efficiency of CS/DNA/gamma-PGA NPs.

Novel method of forming human embryoid bodies in a polystyrene dish surface-coated with a temperature-responsive methylcellulose hydrogel.

A temperature-responsive hydrogel composed of aqueous methylcellulose (MC) blended with distinct concentrations of PBS was prepared and characterized. The developed MC hydrogel underwent a sol-gel reversible transition upon heating or cooling at approximately 32 degrees C. This temperature-responsive hydrogel was employed to coat the surface of a polystyrene dish and used to cultivate human embryonic stem (hES) cell clumps for the formation of embryoid bodies (EBs) in liquid suspension culture (LSC-MC/PS). The conventional hanging drop culture (HDC) and LSC in the uncoated polystyrene dish (LSC-PS) or in the Corning Ultralow-Attachment plate (LSC-ULAP) were used as controls. The results indicated that LSC-PS failed to generate EBs in an efficient manner, whereas the efficiencies of EB formation observed in LSC-ULAP and LSC-MC/PS were significantly greater than in HDC. The hES cells within the EBs were shown to express molecular markers specific for representative cells from the three embryonic germ layers. These results indicated that the MC-coated dish can be used to produce a large scale of hES cell derivatives through the formation of EBs.

Transfer function analysis of ultrasonic time-intensity measurements.

Time-intensity measurements of ultrasonic-contrast microbubbles based on the dilution theory have been used to assist blood flow estimation. The compartment model has been employed to describe the dilution process. Under the linear and time-invariant assumption, the time-intensity curve measured at the output of a compartment (i.e., blood mixing chamber) is the convolution of the input time-intensity curve with the compartment's transfer function. Thus, transfer function analysis is possible using deconvolution when the temporal variations in both the input and the output intensities are available. Note that the linear and time-invariant assumption requires a constant flow rate because, with flow pulsation, the flow rate changes with time and the mixing process becomes time varying. Thus, the purpose of this paper was to study the effects of flow pulsation on time-intensity measurements. In addition, a deconvolution technique based on a recursive least squares approach is used for transfer function analysis. Both simulations and experiments were performed; the results from which indicate that the pulsation generally does not affect the validity of time-intensity-based flow estimation. The proposed deconvolution technique is also effective for both constant and pulsatile flows; thus, permitting transfer function analysis in various flow conditions. One potential application of this transfer function analysis is to remove the effects of a noninstantaneous input function. The results from this paper lead to future work in brain-perfusion estimation based on extracranial time-intensity measurements.

Contrast-specific ultrasonic flow measurements based on both input and output time intensities.

Ultrasonic contrast agents are used to assess perfusion conditions based on evaluation of the time-intensity curve. Such a curve reflects the concentration of microbubbles in the perfused area and the indicator-dilution theory is used to derive the volumetric flow rate from the measured concentration. Previous results have shown that the technique is not reliable in some conditions due to the shadowing effect. To overcome this problem, a contrast-specific technique using both the input and output time-intensity relationships is proposed; this contrasts with conventional techniques that utilize only the relationship directly from the perfused area. The proposed technique is referred to as the input-output time-intensity curve (IOTIC) method. In this work, the shadowing effect was studied experimentally and the efficacy of the IOTIC technique was assessed and compared with conventional techniques. The results indicate that the IOTIC technique eliminates the shadowing effect and provides a good correlation between the actual flow rate and measured flow-related parameters; thus, making quantitative estimation of perfusion feasible. Note that the IOTIC is applicable, based on the assumption that both the input and the output can be positioned within the same image plane; its clinical applications include situations where the perfused area cannot be effectively imaged by ultrasound (US). One example is the assessment of brain perfusion, and it will be used as a target clinical application of the IOTIC technique.