Purified and sterilized magnetosomes from Magnetospirillum gryphiswaldense MSR-1 were not toxic to mouse fibroblasts in vitro

AIMS: To establish a criterion for measuring the purity of purified and sterilized magnetosomes from Magnetospirillum gryphiswaldense and to evaluate their toxicity for mouse fibroblasts in vitro. METHODS AND RESULTS: The purification of magnetosomes involves disrupting bacterial cells with a French Press, washing directly with PBS buffer accompanied by treatment with low power ultrasonication, and using a magnet to collect the magnetosomes. Five characteristic peaks were displayed by Fourier-transform infrared spectroscopy (FT-IR), which was used to detect the quality of the purified magnetosomes, at 3273, 2921, 1735, 1645 and 1531 cm(-1). The purified magnetosomes showed no evidence of impurities when observed by transmission electron microscopy and energy disperse spectroscopy. The particles could be stored at -20 degrees C after lyophilization and treatment by gamma-rays. Purified and sterilized magnetosomes had no obvious negative effects on the viability of mouse fibroblasts by 3-(4,5-dimethylthiazolyl)-2,5-diphenyl-tetrazolium bromide assay. CONCLUSIONS: Purified and sterilized magnetosomes were not toxic to mouse fibroblasts in vitro. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides methods for evaluating the purity and safety of magnetosomes from M. gryphiswaldense. The magnetosomes have the potential to be used as novel drug or gene carriers for tumour therapy.     

Joint modeling and analysis of longitudinal data with informative observation times

Summary .  In analysis of longitudinal data, it is often assumed that observation times are predetermined and are the same across study subjects. Such an assumption, however, is often violated in practice. As a result, the observation times may be highly irregular. It is well known that if the sampling scheme is correlated with the outcome values, the usual statistical analysis may yield bias. In this article, we propose joint modeling and analysis of longitudinal data with possibly informative observation times via latent variables. A two-step estimation procedure is developed for parameter estimation. We show that the resulting estimators are consistent and asymptotically normal, and that the asymptotic variance can be consistently estimated using the bootstrap method. Simulation studies and a real data analysis demonstrate that our method performs well with realistic sample sizes and is appropriate for practical use.     

极端干旱区胡杨根系吸水的二维数学模型

依据在极端干旱区额济纳旗的实测资料,对胡杨根系及根区土壤水分特征进行了分析,借鉴国内外成熟的植物根系吸水模型,建立了胡杨根系吸水的二维数学模型。模型结果与实测结果平均相对误差为9.02%,最大相对误差为17.84%。所建模型基本反映了胡杨根系吸水的实际状况,对胡杨根系分布、吸水及胡杨SPAC系统进一步的研究提供了有益的参考。     

Effect of Boron on Osteogenic Differentiation of Human Bone Marrow Stromal Cells

Bone marrow stromal cells (BMSCs) have been well established as an ideal source of cell-based therapy for bone tissue engineering applications. Boron (B) is a notable trace element in humans; so far, the effects of boron on the osteogenic differentiation of BMSCs have not been reported. The aim of this study was to evaluate the effects of boron (0, 1, 10,100, and 1,000?ng/ml) on osteogenic differentiation of human BMSCs. In this study, BMSCs proliferation was analyzed by cell counting kit-8 (CCK8) assay, and cell osteogenic differentiation was evaluated by alkaline phosphatase (ALP) activity assay, Von Kossa staining, and real-time PCR. The results indicated that the proliferation of BMSCs was no different from the control group when added with B at the concentration of 1, 10, and 100?ng/ml respectively (P?>?0.05); in contrast, 1,000?ng/ml B inhibited the proliferation of BMSCs at days?4, 7, and 14 (P?相似文献   

Cloning and expression pattern of the human NDRG3 gene

We report the cloning and expression pattern of a novel N-myc downstream-regulated gene 3 (NDRG3), located on human chromosome 20q11.21-11.23. The NDRG3 cDNA is 2588 base pair in length, encoding a 363 amino acid polypeptide highly related to mouse Ndr3 protein. Northern blot reveals that NDRG3 is highly expressed in testis, prostate and ovary. By in situ hybridization, the NDRG3 mRNA was localized to the outer layers of seminiferous epithelium, indicating that it may play a role in spermatogenesis.     

植物蛋白酶抑制剂基因结构、调控及其控制害虫的策略

各种不同类型的植物蛋白酶抑制剂基因已被分离,它们的特异产物(单基因或多基因组合),对昆虫体内各种生化和生理过程会产生不同程度的影响,在对昆虫和病原体防御体系中起重要作用。多种蛋白酶抑制剂重组,协同保护植物的方法,已成为害虫综合防治计划的一部分。尽管它们近期内尚不能代替化学杀虫剂,但可作为有效的替补。目前,大多数抑制剂的作用和机理正在详尽地研究中,该文综述了植物蛋白酶抑制剂的基因结构、调控与表达并讨论了培育转基因作物控制害虫的策略。     

The effect of clinical-grade retinal pigment epithelium derived from human embryonic stem cells using different transplantation strategies

Dear Editor, Many forms of sight-threatening diseases, including retinitis pigmentosa (RP) and age-related macular degeneration (AMD), are caused by the dysfunction, degeneration and loss of the retinal pigment epithelium (RPE)(Strauss, 2005). RPE cell transplantation may potentially recover or halt disease progression, in which human embryonic stem cells (hESCs) could serve as an unlimited donor source for RPE differentiation, and a few clinical trials have shown the safety and effective of transplantation of hESCs-derived RPE (hESC-RPE) for AMD patients (Schwartz et al., 2012;Schwartz etal., 2015;Song etal., 2015;da Cruz et al., 2018;Kashani et al., 2018;Liu et al., 2018).     

Engineering of a genome-reduced host: practical application of synthetic biology in the overproduction of desired secondary metabolites

Synthetic biology aims to design and build new biological systems with desirable properties, providing the foundation for the biosynthesis of secondary metabolites. The most prominent representation of synthetic biology has been used in microbial engineering by recombinant DNA technology. However, there are advantages of using a deleted host, and therefore an increasing number of biotechnology studies follow similar strategies to dissect cellular networks and construct genome-reduced microbes. This review will give an overview of the strategies used for constructing and engineering reduced-genome factories by synthetic biology to improve production of secondary metabolites.     

Sequences near both termini of the C/EBPβ mRNA 3＇ untranslated region are important for its tumor suppression activity

The 3＇ untranslated region （3＇ UTR） of eukaryotic mRNA is an important regulation element that affects not only mRNA translation, but also cell growth. We had found that the 3＇ UTR of CCAAT-enhancerbinding protein β （C/EBPβ） mRNA had tumor suppression activity. Herein, we reported that deletion of two short sequences at both termini of the C/EBPβ 3t UTR reduced the tumor suppression activity of this 3＇ UTR, as demonstrated by reduced cell growth, colony formation ability, and tumorigenicity in nude mice. It is noteworthy that the only deletion of a single such sequence was enough for the reduction of tumor sup- pression effect, and the reducing effect of deletion of the sequence near 3r terminus was stronger. Therefore, specific short sequences in the C/EBPβ 3＇ UTR are crucial for the tumor suppression activity of C/EBPβ.