Heterogeneous to homogeneous melting transition visualized with ultrafast electron diffraction

The ultrafast laser excitation of matters leads to nonequilibrium states with complex solid-liquid phase-transition dynamics. We used electron diffraction at mega-electron volt energies to visualize the ultrafast melting of gold on the atomic scale length. For energy densities approaching the irreversible melting regime, we first observed heterogeneous melting on time scales of 100 to 1000 picoseconds, transitioning to homogeneous melting that occurs catastrophically within 10 to 20 picoseconds at higher energy densities. We showed evidence for the heterogeneous coexistence of solid and liquid. We determined the ion and electron temperature evolution and found superheated conditions. Our results constrain the electron-ion coupling rate, determine the Debye temperature, and reveal the melting sensitivity to nucleation seeds.

Model research on repairing meniscus injury in rabbits using bone marrow mesenchymal stem cells and silk fibroin meniscus porous scaffold

OBJECTIVE

The purpose of this study is to evaluate the histocompatibility and feasibility of structure and function of bone marrow mesenchymal stem cells (BMSCs) and silk fibroin meniscus porous scaffolds in repairing meniscus injury in rabbits.

MATERIALS AND METHODS

BMSCs were cultured and identified in vitro, silk fibroin meniscus porous scaffolds were prepared and the histocompatibility of porous scaffolds was evaluated via in vitro culture. Silk fibroin-BMSCs porous scaffolds were implanted into the meniscus defect area of New Zealand white rabbits as the experimental group, the blank scaffold group without BMSCs, pure BMSCs group and blank control group were set up with 10 rabbits in each group. Joint capsules were opened for general observation at 6 weeks and 12 weeks after operation. The specimens received the HE staining, alkaline toluidine blue staining, and immunohistochemical staining of Type I and Type II collagen and S100 protein.

RESULTS

In vitro HE staining and SEM observation showed that the scaffolds showed the sponge-like structure with abundant microporous structure on the surface and inside, which had a good histocompatibility with BMSCs. At 6 and 12 weeks after operation in experimental group, meniscus-like tissues were found in the meniscus defect area. HE staining showed the fibrous cartilage-like structure and obvious collagenous fiber structure around arranged in an orderly manner. Alkaline toluidine blue staining showed the cartilage-specific glycosaminoglycan (GAG); Type I and Type II collagen and S100 protein staining were strongly positive. However, the above changes were not seen in other groups.

CONCLUSIONS

BMSCs and silk fibroin meniscus porous scaffolds have a better histocompatibility and feasibility of structure and function in repairing meniscus injury in rabbits.

The long noncoding RNA BC0209135 inhibits the cell invasion through Wnt/β-catenin signaling in colorectal cancer

OBJECTIVE

Previous studies have shown that BC029135, a long noncoding RNA (lncRNA) with high conservation, was decreased with high fold change in colorectal cancer (CRC) by using microarray assay. In the present work, we investigated the functions of BC029135 in CRC, as well as the potential mechanisms underlying the malignant phenotype caused by loss of BC029135.

MATERIALS AND METHODS

Bioinformatics analysis of lncRNA BC029135 was performed to identify the potential function. The cell lines of HCT-116, SW480, SW620, LoVo, SW1116, and HT29 were used in this study. The mRNA expression of BC029135 and β-actinin was measured by Real-Time Polymerase Chain Reaction (RT-PCR). Western blot analysis was used to determine protein expression of β-actinin, MMP-2, cyclin D1, and c-Myc.

RESULTS

Our research showed that the expression of BC029135 in CRC tissues and cell lines was significantly lower than in adjacent normal tissues. In addition, overexpression of lncRNA BC029135 could inhibit the invasion of CRC cells. We also found that lncRNA BC029135 inhibits Wnt/β-catenin signaling in CRC cell lines.

CONCLUSIONS

We suggest that up-regulation of BC029135 suppresses CRC invasion and inactivates Wnt/β-catenin signaling. It will provide new insights for the treatment of colorectal cancer and new clues for clinical treatment.

Preparation and Properties of 3D Printed Alginate⁻Chitosan Polyion Complex Hydrogels for Tissue Engineering

Three-dimensional (3D) printing holds great potential for preparing sophisticated scaffolds for tissue engineering. As a result of the shear thinning properties of an alginate solution, it is often used as 3D printing ink. However, it is difficult to prepare scaffolds with complexity structure and high fidelity, because the alginate solution has a low viscosity and alginate hydrogels prepared with Ca2+ crosslinking are mechanically weak. In this work, chitosan powders were dispersed and swelled in an alginate solution, which could effectively improve the viscosity of an alginate solution by 1.5⁻4 times. With the increase of chitosan content, the shape fidelity of the 3D printed alginate⁻chitosan polyion complex (AlCh PIC) hydrogels were improved. Scanning electron microscope (SEM) photographs showed that the lateral pore structure of 3D printed hydrogels was becoming more obvious. As a result of the increased reaction ion pairs in comparison to the alginate hydrogels that were prepared with Ca2+ crosslinking, AlCh PIC hydrogels were mechanically strong, and the compression stress of hydrogels at a 90% strain could achieve 1.4 MPa without breaking. In addition, human adipose derived stem cells (hASCs) adhered to the 3D printed AlCh PIC hydrogels and proliferated with time, which indicated that the obtained hydrogels were biocompatible and could potentially be used as scaffolds for tissue engineering.

3D uniaxial mechanical stimulation induces tenogenic differentiation of tendon-derived stem cells through a PI3K/AKT signaling pathway

The tendon is a mechanosensitive tissue, but little is known about how mechanical stimulation selectively signals tenogenic differentiation and neo-tendon formation. In this study, we compared the impact of uniaxial and biaxial mechanical loading on tendon-derived stem cells (TDSCs). Our data show that there are variations in cell signaling and cell differentiation of mouse TDSCs in response to uniaxial and biaxial loading in monolayer culture. Whereas uniaxial loading induced TDSCs toward tenogenic and osteogenic differentiation, biaxial loading induced osteogenic, adipogenic, and chondrogenic differentiation of TDSCs. Furthermore, by applying uniaxial loading on 3-dimensional (3D) TDSC constructs, tenogenic-specific differentiation and neo-tendon formation were observed, results that were replicated in human TDSCs. We also showed that uniaxial loading induced PKB (AKT) phosphorylation (pAKT), whereas biaxial loading induced pERK. Most importantly, we found that inhibition of the PI3K/AKT signaling pathway could attenuate tenogenic differentiation and tendon formation in 3D TDSC constructs subjected to uniaxial loading. Taken together, our study highlights the importance of appropriate mechanobiological stimulation in 3D cell niches on tendon-like tissue formation and demonstrates that uniaxial mechanical loading plays an essential role in tenogenic differentiation and tendon formation by activating the PI3K/AKT signaling pathway.-Wang, T., Thien, C., Wang, C., Ni, M., Gao, J., Wang, A., Jiang, Q., Tuan, R. S., Zheng, Q., Zheng, M. H. 3D uniaxial mechanical stimulation induces tenogenic differentiation of tendon-derived stem cells through a PI3K/AKT signaling pathway.

In vitro loading models for tendon mechanobiology

Tendons are the connective tissue responsible for transferring force from muscles to bones. A key factor in tendon development, maturation, repair, and degradation is its biomechanical environment. Understanding tendon mechanobiology is essential for the development of injury prevention strategies, rehabilitation protocols and potentially novel treatments in tendon injury and degeneration. Despite the simple overall loading on tendon tissue, cells within the tissue in vivo experience a much more complex mechanical environment including tension, compression and shear forces. This creates a substantial challenge in the establishment of in vitro loading models of the tendon. This article reviews multiple loading models used for the study of tendon mechanobiology and summarizes the main findings. Although impressive progress has been achieved in the functionality and mimicry of in vitro loading models, an ideal platform is yet to be developed. Multidisciplinary approaches and collaborations will be the key to unveiling the tendon mechanobiology. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:566-575, 2018.

Comparative efficacy of five long-term weight loss drugs: quantitative information for medication guidelines

Quantitative information is scarce in current obesity medication guidelines, and they do not clearly reflect the differences in the efficacy characteristics among various drugs. This study quantitatively assessed the efficacy characteristics of five FDA-approved long-term weight loss drugs. Potentially eligible studies were obtained from public databases. Using the differences in the weight change from baseline between the drug group and the corresponding placebo group as the major indicator of efficacy, a time-effect model was established, and crucial pharmacodynamic parameters, such as the maximal efficacy, drug onset time and rate of body weight regain after the maximal efficacy point, were used to reflect the differences in efficacy among the five drugs. Finally, 50 reports (involving 43,443 participants) were included. After deducting the placebo effects, the maximal efficacies (95% CI) of orlistat (120 mg), lorcaserin, naltrexone-bupropion, phentermine-topiramate (PT, 7.5/46 mg) and liraglutide were -2.94 (-5.82, -1.27), -3.06 (-4.39, -1.71), -6.15 (-9.78, -3.25), -7.45 (-9.76, -3.88) and -5.50 (-10.62, -2.97) kg at weeks 60, 54, 67, 59 and 65 respectively, and their rates of body weight regain were 0.51, 0.48, 0.91, 1.27and 0.43 kg per year respectively. The 1-year dropout rates of orlistat, lorcaserin, naltrexone-bupropion, PT and liraglutide were 29.0, 40.9, 49.1, 34.9 and 24.3% respectively. In addition, a significant dose-effect correlation was observed for orlistat and PT. This study provides valid quantitative information for medication guidelines.

Electron-lattice energy relaxation in laser-excited thin-film Au-insulator heterostructures studied by ultrafast MeV electron diffraction

We apply time-resolved MeV electron diffraction to study the electron-lattice energy relaxation in thin film Au-insulator heterostructures. Through precise measurements of the transient Debye-Waller-factor, the mean-square atomic displacement is directly determined, which allows to quantitatively follow the temporal evolution of the lattice temperature after short pulse laser excitation. Data obtained over an extended range of laser fluences reveal an increased relaxation rate when the film thickness is reduced or the Au-film is capped with an additional insulator top-layer. This behavior is attributed to a cross-interfacial coupling of excited electrons in the Au film to phonons in the adjacent insulator layer(s). Analysis of the data using the two-temperature-model taking explicitly into account the additional energy loss at the interface(s) allows to deduce the relative strength of the two relaxation channels.

Efficacy of the Wallis interspinous implant for primary lumbar disc herniation : a prospective randomised controlled trial

To investigate the efficacy of the Wallis implant after lumbar discectomy compared with discectomy alone for primary lumbar disc herniation. Seventy-seven patients with primary lumbar disc herniation were randomly assigned to undergo either posterior lumbar discectomy with (n=40, Wallis group) or without (n=37, control group) Wallis implantation. The primary outcomes were visual analogue scale score, Japanese Orthopedics Association score, and Oswestry Disability Index. The secondary outcomes were intervertebral disc height, range of motion of the operated segments, complications, and operating time. The primary outcomes at 1 week after treatment (P> 0.05) were not different between groups. The Wallis group had better scores at 12 months (P< 0.05) and the last follow-up visit (P< 0.05), higher disc height (P< 0.001), and significantly longer operating time (P =0.006) than the control group. Combined treatment appears beneficial for pain relief and lumbar function improvement by maintaining intervertebral disc height and limiting the range of motion of the spine compared with lumbar discectomy alone. However, its actual clinical benefit remains controversial because of the longer operating time and the relatively small difference in the visual analogue scale score and Oswestry Disability Index between the groups.

Quantitative analysis of efficacy and associated factors of calcium intake on bone mineral density in postmenopausal women

A model-based meta-analysis method was performed to quantitatively analyze the efficacy characteristics of calcium intake in BMD increase among postmenopausal women. We found that age and calcium intake dose were key factors affecting the efficiency and onset of BMD change, and daily 1200 mg calcium was suggested to be a beneficial dosage.

INTRODUCTION

This paper aims to quantify the efficacy of calcium intake in preventing bone mineral density (BMD) decrease among postmenopausal women and to investigate the factors that may affect the efficacy.

METHODS

Comprehensive literature search was conducted in PubMed and EMBASE from January 2016. Placebo-controlled or no-treatment controlled randomized trials focused on calcium intake for the management of osteoporosis in postmenopausal women were included. The clinical and demographic characteristics of participants and efficacy data, defined as the mean percentage change of spine BMD (L2-L4) at each observation time point compared with that of baseline, were extracted from the studies. Model-based meta-analysis (MBMA) was used to describe the time course of BMD change by calcium intake and identify the related factors.

RESULTS

This study includes 17 trials involving 2537 subjects. The results showed that a classic pharmacodynamic maximal effect (E _max) model could describe the time course of BMD change by calcium intake. Using this model, we found that age and calcium intake dose were key factors affecting the efficiency and onset of BMD change. A 60-year-old woman administered with 800 mg/day calcium can achieve a maximum BMD increasing rate of 2.38%, and the time to reach 50% of this maximum (known as onset time) was 9.44 months. An increase of 0.0817% per year was noted in the maximal effect value for women aged between 50 and 83 years. For calcium dose interval from 250 to 2000 mg/day, the onset time was expressed as 9.44 × (dose/800)^-1.33 months. Two-year calcium intake of 700, 1200, and 2000 mg/day resulted in a maximum efficacy of BMD of 68.0, 81.3, and 89.6%, respectively. This indicates that the final efficacy had already reached the plateau (>80% E _max) under the 1200-mg/day dose.

CONCLUSION

Calcium intake can effectively postpone the tendency of BMD decrease in postmenopausal women. An increased calcium dose contributes to the shortening of the onset time. Considering the drug-acting rate and safety into account, menopausal women can be administered with a rational dose of 1200 mg/day to reduce bone loss.