High Density Lipoprotein Protects Mesenchymal Stem Cells from Oxidative Stress-Induced Apoptosis via Activation of the PI3K/Akt Pathway and Suppression of Reactive Oxygen Species

The therapeutic effect of transplantation of mesenchymal stem cells (MSCs) in myocardial infarction (MI) appears to be limited by poor cell viability in the injured tissue, which is a consequence of oxidative stress and pro-apoptotic factors. High density lipoprotein (HDL) reverses cholesterol transport and has anti-oxidative and anti-apoptotic properties. We, therefore, investigated whether HDL could protect MSCs from oxidative stress-induced apoptosis. MSCs derived from the bone marrow of rats were pre-incubated with or without HDL, and then were exposed to hydrogen peroxide (H2O2) in vitro, or were transplanted into experimentally infarcted hearts of rats in vivo. Pre-incubation of MSCs with HDL increased cell viability, reduced apoptotic indices and resulted in parallel decreases in reactive oxygen species (ROS) in comparison with control MSCs. Each of the beneficial effects of HDL on MSCs was attenuated by inhibiting the PI3K/Akt pathway. Preconditioning with HDL resulted in higher MSC survival rates, improved cardiac remodeling and better myocardial function than in the MSC control group. Collectively, these results suggest that HDL may protect against H2O2-induced apoptosis in MSCs through activation of a PI3K/Akt pathway, and by suppressing the production of ROS

Subtelomeric assembly of a multi-gene pathway for antimicrobial defense compounds in cereals

Non-random gene organization in eukaryotes plays a significant role in genome evolution. Here, we investigate the origin of a biosynthetic gene cluster for production of defence compounds in oat—the avenacin cluster. We elucidate the structure and organisation of this 12-gene cluster, characterise the last two missing pathway steps, and reconstitute the entire pathway in tobacco by transient expression. We show that the cluster has formed de novo since the divergence of oats in a subtelomeric region of the genome that lacks homology with other grasses, and that gene order is approximately colinear with the biosynthetic pathway. We speculate that the positioning of the late pathway genes furthest away from the telomere may mitigate against a ‘self-poisoning’ scenario in which toxic intermediates accumulate as a result of telomeric gene deletions. Our investigations reveal a striking example of adaptive evolution underpinned by remarkable genome plasticity

Mechanical properties of grafold: a demonstration of strengthened graphene

NSF of China [11074039]; National Key Project for Basic Research of China [2011CBA- 00200]; 2009 Project for Scientific and Technical Development of Xiamen [3502Z20099007]Morphological patterns and structural features play crucial roles in the physical properties of functional materials. In this paper, the mechanical properties of grafold, an architecture of folded graphene nanoribbon, are investigated via molecular dynamics simulations and intriguing features are discovered. In contrast to graphene, grafold is found to develop large deformations upon both tensile and compressive loading along the longitudinal direction. The tensile deformation is plastic, whereas the compressive deformation is elastic and reversible within the strain range investigated. The calculated Young's modulus, tensile strength, and fracture strain are comparable to those of graphene, while the compressive strength and strain are much higher than those of graphene. The length, width, and folding number of grafold have distinctive impacts on the mechanical performance. These unique behaviors render grafold a promising material for advanced mechanical applications

A molecular dynamics investigation of the mechanical properties of graphene nanochains

NSF of China [11074039]; National Key Project for Basic Research of China [2011CBA00200]; Program for Changjiang Scholars and Innovative Research Team in University [IRT1115]; Fujian Education Bureau [GB11022]In this paper, we investigate, by molecular dynamics simulations, the mechanical properties of a new carbon nanostructure, termed a graphene nanochain, constructed by sewing up pristine or twisted graphene nanoribbons (GNRs) and interlocking the obtained nanorings. The obtained tensile strength of defect-free nanochain is a little lower than that of pristine GNRs and the fracture point is earlier than that of the GNRs. The effects of length, width and twist angle of the constituent GNRs on the mechanical performance are analyzed. Furthermore, defect effect is investigated and in some high defect coverage cases, an interesting mechanical strengthening-like behavior is observed. This structure supports the concept of long-cable manufacturing and advanced material design can be achieved by integration of nanochain with other nanocomposites. The technology used to construct the nanochain is experimentally feasible, inspired by the recent demonstrations of atomically precise fabrications of GNRs with complex structures [Phys. Rev. Lett., 2009, 102, 205501; Nano Lett., 2010, 10, 4328; Nature, 2010, 466, 470]

Silicon-Rich Biochar Detoxify Multiple Heavy Metals in Wheat by Regulating Oxidative Stress and Subcellular Distribution of Heavy Metal

Silicon is a quasi-essential trace nutrient for plant growth and is frequently employed to remediate soils of heavy metal pollution in agriculture. However, silicon’s role and mechanism in reducing heavy metal toxicity have not been well understood, especially for multi-heavy metals such as cadmium, zinc, lead, and arsenic (usually treated as a heavy metal). In this study, the effects of different silicon-rich materials (silicate, rice husk biochar (RHB), and RHB + bentonite) on growth trait, antioxidant response, heavy metal accumulation, and distribution of wheat grown in two soils polluted by multiple heavy metals (Cd, Zn, Pb, and As) were investigated. The results revealed that the addition of silicon-rich materials enhanced plant growth, improved the photosynthetic attributes in leaf tissues, and decreased the contents of Cd, Zn, Pb, and As in wheat shoots and grains. The examination of the subcellular distribution of heavy metals in plants implied that silicon-rich materials transferred heavy metals as intracellular soluble fractions to the cell walls, indicating the reduction of mobility and toxicity of heavy metals in the plants. In addition, the application of the silicon-rich materials reduced oxidative damage in plants by downregulating plant antioxidant response systems and decreasing the production of malondialdehyde (MDA), ascorbic acid (AsA), and glutathione (GSH). Moreover, fractionation analysis of soil heavy metals showed that silicon-rich amendments could convert bioavailable heavy metals into immobilized forms. With the comparation of different silicon-rich materials, combined RHB and bentonite could better remediate multi-heavy metal-polluted soils and promote wheat production. The effect of the silicate component was stressed in this paper but some of the potential benefits might have arisen from other components of the biochar

Structural and electronic properties of c-BC2N supper hard material: An ab initio study

Conference Name:2011 International Conference on Frontier of Nanoscience and Technology, ICFNST 2011. Conference Address: Kunming, China. Time:September 28, 2011 - September 29, 2011.In this paper, first-principles calculations are performed to study the influence of atomic design on the structural and electronic properties of pseudo-cubic BC2N. The calculated results indicate that atomic structures and bond configurations have significant effects on the electronic properties. From band structure and total density of state, it is found that there exist five semiconductor configurations and two semi-metal configurations in pesudo-cubic BC2N. Within LDA approximation, the predicted band gaps vary from 0.7 eV to 2.6 eV for the five semiconductor configurations. A recently proposed band gap calculation method, termed Δ-sol method, is applied to correct the obtained energy band gaps, and the corrected range is from 2.9 eV to 4.4 eV. These results indicate that the band gap tuning in super hard materials can be implemented via atomic design