Crack mechanism and experimental verification on straightening of AZ31B magnesium alloy plate.

When plates with edge cracks in the rolling process is straightened by cyclic tensile and compressive stress, the tip of edge crack always accompanied by stress concentration, which leads to crack propagation. In this paper, damage parameters are imported into the plate straightening model based on determining the GTN damage parameters of magnesium alloy materials by inverse finite element calibration method, the influence of different straightening process schemes and prefabricated V-shaped crack geometry on crack growth is analyzed through the way of the combination of simulation and straightening experiment. The results show that the peak values of equivalent stress and equivalent strain under each straightening roll appear at the crack tip. The value of longitudinal stress and equivalent stain decrease with the distance to crack tip becomes larger. The peak value of longitudinal stress appears when the crack circumferential angle is about 100°, and the crack tip is easy to form crack propagation; when the plate passes roll 2 and roll 4, the equivalent stress and strain concentration at the crack tip are most obvious; when the reduction reaches a certain degree, the void volume fraction (VVF) reaches the VVF of the material breaking; with the increase of the entrance reduction, the number of VVF at the crack tip which reaches the material fracture increases, and the length of crack propagation increases; the stress concentration at the tip of V-shaped crack with large length-width ratio is obvious, and the VVF is more likely to reach the VVF at the time of material fracture, crack initiates and propagates easily.

[Down-Regulation of MiR-125b Reverses Drug Resistance of Doxorubicin-Resistant Leukemia Cells].

OBJECTIVE: To investigate whether the down-regulation of miR-125b can reverse the drug-resistence of doxorubicine-resistant leukemia cell lines or not, so as to explore a new method for treatment of drug-resistant leukemia patients. METHODS: The expression levels of miR125b in doxorubicine drug-sensitive and doxorubicine drug-resistant leukemia cell lines.HL-60, K562 and HL-60/Dox, the K562/Dox were detected by using RT-qPCR; the up-regulation or inhibition of miR-1256 expression in HL-60/Dox were performed by electroporation transfection, then the viability of cells treated with doxorubicine of different concentration was detected by CCK-8 method, the proliferation inhibition curve of cells was drawed, and the IC50 was calculated. RESULTS: The miR-125b expression was obviously up-regulated in drug-resistant cell lines HL-60/DOX and K562/DOX, as compared with HL-60 and K562 cell lines. The miR-125b expression level in HL-60/DOX and K562/DOX cells was 15 times and 5 times higher than that in HL-60 and K562 cells, respectively. The up-regulating or inhibiting expression of miR-125b in HL-60/DOX cells found that the proliferation inhibition rate in cells transfected with miR-125b mimic significantly decreased, compared with control group (P<0.01), while the proliferation inhibition rate in cells transfected with miR-125b inhibitor significantly increased, compared with control group(P<0.01). CONCLUSION: The miR-125b expression in HL-60/Dox and K562/Dox cells has been up-regulated, down-regulation of miR-125b expression can reverse the drug resistance of leukemia cells to doxorubicine.

Hsa_circ_0007534/miR-761/ZIC5 regulatory loop modulates the proliferation and migration of glioma cells.

Increasing evidences demonstrate the essential roles of circular RNAs (circRNAs) in human cancers. However, the study about the functions of circRNAs in glioma remains very limited. In the present study, we found that circRNA hsa_circ_0007534 was highly expressed in glioma tissues compared to normal brain tissues. Furthermore, we found that knockdown of hsa_circ_0007534 significantly inhibited the proliferation and migration of glioma cells. In mechanism, we showed that hsa_circ_0007534 could sponge miR-761 to repress its availability in glioma cells. We found that inhibition of miR-761 could rescue the suppressed proliferation and migration of glioma cells by hsa_circ_0007534 knockdown. Moreover, we explored the downstream mechanism and found that ZIC5 was a target of miR-761. We showed that hsa_circ_0007534 promoted the expression of ZIC5 by inhibiting miR-761 in glioma cells. And restoration of ZIC5 expression significantly reversed the effects of hsa_circ_0007534 knockdown on glioma cell proliferation and migration. In summary, our results demonstrated that hsa_circ_0007534 serves as an oncogene in glioma via promoting ZIC5 expression by repressing miR-761 availability. Our results suggested that hsa_circ_0007534/miR-761/ZIC5 regulatory loop might be a promising therapeutic target for glioma treatment.

Inhibition of microRNA-34a protects against propofol anesthesia-induced neurotoxicity and cognitive dysfunction via the MAPK/ERK signaling pathway.

AIM: To investigate the protective effect of microRNA-34a (miR-34a) on propofol-induced neurotoxicity and cognitive dysfunction. METHODS: After SH-SY5Y cells were treated with propofol to induce neurotoxicity, microRNA-34a mimics and inhibitors were transfected into the cells. The expression of apoptosis-related genes and the proteins were measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blot. Sprague-Dawley (SD) rats received intraperitoneal injections of propofol, and were treated with microRNA-34a mimics and lentivirus-mediated microRNA-34a inhibitors. The Morris water maze (MWM) test was used to detect changes in motor function. RESULTS: Propofol anesthesia had an adverse effect on cell survival due to the increased expression of apoptosis-related genes such as cleaved caspase-3/8 and Bax, which was accompanied by reduced expression of ERK1/2, pERK1/2, and phosphorylated NF-kappaB p65 both in vivo and in vitro. Unexpectedly, microRNA-34a was upregulated after propofol treatment, and the inhibitors protected the SH-SY5Y cells from propofol-induced apoptosis. The microRNA-34a inhibitor suppressed the apoptosis-induced effects of propofol. This protection may have been partly diminished by PD98059, a MAPK kinase inhibitor. MicroRNA-34a inhibited or reverted the reduced expression of ERK1/2 and upregulated the expression of p-CREB significantly and specifically. Additionally, the microRNA inhibitors improved the learning and memory functions of animals suffering from neurologic impairment due to propofol treatment and reduced cell apoptosis in the hippocampus. CONCLUSION: microRNA-34a could improve anesthesia-induced cognitive dysfunction by suppressing cell apoptosis and recovering the expression of genes associated with the MAPK/ERK signaling pathway.

Long-Term Efficacy of Initial Microvascular Decompression Versus Subsequent Microvascular Decompression for Idiopathic Hemifacial Spasm.

OBJECTIVE: Hemifacial spasm (HFS) is a disorder characterized by intermittent, involuntary facial muscle contractions. Microvascular decompression (MVD) is the gold treatment for HFS. The aim of this research was to discuss whether patients undergoing MVD as their initial surgical intervention experience greater spasm control than patients experiencing an MVD performed as a subsequent surgical intervention. METHODS: The study included 976 patients with HFS, 452 of whom (group A) underwent MVD as their initial surgical intervention and 524 of whom (group B) underwent subsequent MVD. Relevant clinical data including outcome of MVD, operative findings, complications, and so on were collected immediately after MVD operation and at follow-up. RESULTS: The follow-up period was 7-9 years (mean, 7.96 ± 0.87 years). The mean age at intervention was 53.14 years and 55.43 years in the 2 groups, respectively. The long-term postoperative relief rate of patients in the 2 groups was 98.23% and 87.21%, respectively. There was a significant difference in long-term postoperative relief rate of patients between the 2 groups (P < 0.05). CONCLUSIONS: Patients undergoing MVD for HFS as the primary treatment experience better long-term efficacy than patients first treated with botulinum neurotoxin type A.

Preparation and testing of quaternized chitosan nanoparticles as gene delivery vehicles.

The aim of this study was to synthesize a chitosan (CS) derivative, a quaternary ammonium salt crystal called N-2-hydroxypropyl trimethyl ammonium chloride chitosan (HACC), and test a series of HACC and pEGFP-DNA complexes at different weight ratios for their efficiency of gene delivery into human cells. CS was modified with cationic etherifying agent to obtain the CS derivative. Fourier transform infrared spectra were recorded on KBr pellets with a spectrometer. (1)H nuclear magnetic resonance (NMR) spectra of HACC were obtained using a spectrometer. HACC was subsequently used to prepare HACC/DNA complexes at different weight ratios by coacervation method. The resulting particle size and surface charge were assessed by laser light scattering using a zeta potential analyzer. The HACC/DNA complex formation and DNA protection in the nanoparticle complex was investigated by gel mobility shift assay and DNase I protection assay, respectively. The cytotoxicity of HACC and HACC/DNA nanoparticles was evaluated by MTT assay using (mesenchymal stem cell) MSC lines. The nanoscale structure of the particles was obtained by transmission electron microscope (TEM). The FTIR spectrum of HACC showed the characteristic quaternary ammonium group absorption band at 1475 cm(-1), which indicated the presence of quaternary ammonium group. The successful synthesis of HACC was also confirmed by (1)H NMR spectrum. HACC showed good solubility in water and was electropositive. HACC efficiently packed and protected pEGFP-DNA at a weight ratio of 10. With increased weight ratios, the surface charge of the composite particle increased from negative to positive, the average particle size increased, and HACC nanoparticle had a higher carrying efficiency. The nanoparticles released DNA in two distinct phases, and 55 % was released within the first 20 h of solubilization. The nanoparticles under TEM showed circular or oval shapes. The particles exhibited no cytotoxicity against human cells. No significant difference in gene delivery efficiency was detected between HACC/pEGFP-GDNF and liposome/pEGFP-GDNF complexes (33.8 vs. 34 %, P = 0.363). In this study, HACC was successfully synthesized, and HACC/DNA complex assembled efficiently. HACC showed strong DNA binding affinity and high protection of DNA and was non-cytotoxic to human cells. The particles had appropriate nanostructure, mean diameter, and DNA release time. The results suggest that HACC nanoparticles are a novel tool for efficient and safe gene delivery.

Repair of acute injuries of the lateral ligament complex of the ankle by suture anchors.

OBJECTIVE: The objective of this study was to investigate the clinical curative effect of stage I repair of acute injuries of the lateral ligament complex of the ankle by the application of suture anchors. METHODS: We retrospectively analyzed 18 cases of III degree acute injuries of the lateral ligament complex of the ankle. RESULTS: There were statistically significant differences in preoperative and last follow-up VAS pain scores and AOFAS ankle hind-foot function scores. The X-ray talus displacement values in the anterior drawer test and pressure anteroposterior X-ray talar tilt in the ankle talar tilt test also showed statistically significant differences. Complications occurred in 2 patients, incision surface infection in one, and postoperative lateral dorsal skin numbness in one. All these cases were cured after symptomatic treatment. At the last follow-up all patients' ankle joint activity recovered to their preinjury function levels. CONCLUSION: The application of suture anchors for small incision stage I repair of the lateral collateral ligament of ankle joint degree III injury, can effectively restored the stability of ankle joint, and prevent the occurrence of chronic ankle instability complications. It is effective and feasible for the treatment of ankle joint lateral collateral ligament injuries.