ABSTRACT
BACKGROUND: It has been confirmed that a polymer scaffold with hydroxyapatite (HA) has good biocompatibility. Chitosan that is combined with other materials, such as HA, hyaluronic acid, alginate, and potential growth factors, can be applied in tissue engineering field. Meanwhile, numerous studies have confirmed that bone morphogenetic protein-2 (BMP-2)can promote the growth of osteoblasts and induce osteogenesis in vitro and in vivo.So,can we prepare a new tissue-engineered scaffold with these four kinds of materials? OBJECTIVE: To prepare a novel BMP-2-loaded tissue-engineered bone scaffold using poly(lactic-co-glycolic acid) (PLGA), HA and different concentrations of chitosan, and to observe the scaffold structure, hydrophilicity, and adherence to osteoblasts as well as the optimal modification concentration of chitosan. METHODS: (1) A tissue-engineered scaffold containing PLGA, HA and BMP-2 was prepared using the solid-liquid phase separation and modified by chitosan (0.25%, 0.5% and 1%). Additionally, PLGA/HA and PLGA/HA/BMP-2 scaffolds were prepared as controls. Scaffold structure was observed under a scanning electron microscope. The hydrophilicity of each scaffold and BMP-2 release of the PLGA/HA/BMP-2/chitosan scaffold were examined. (2) Pre-osteoblastic suspensions were seeded onto each scaffold. Cell adhesion and proliferation were detected using cell counting kit-8 at 1, 4, 7 days of cell culture. Fluorescein diacetate was used for a vital staining of cells at 7 days of cell culture. Alkaline phosphatase activity was detected at 4, 7 and 14 days of cell culture. RESULTS AND CONCLUSION: (1) All the scaffolds were white beaker-shaped and had porous structure with a pore size of about 100 μm, and interconnected pores were observed under the scanning electron microscope. (2) The scaffold hydrophilicity was increased with the increasing concentration of chitosan. (3) BMP-2 cumulative release amount was 44% for the PLGA/HA/BMP-2, 34% for PLGA/HA/BMP-2/0.25% chitosan, 27% for PLGA/HA/BMP-2/0.5% chitosan, and 26% for PLGA/HA/BMP-2/1% chitosan, indicating that chitosan can effectively slow the release of BMP-2. (4) Cell viability of pre-osteoblasts seeded onto the PLGA/HA/BMP-2/0.25% chitosan scaffold was highest at 7 days of cell culture. Higher cell viability of pre-osteoblasts seeded onto the PLGA/HA/BMP-2/chitosan (0.5%, 1%) scaffolds was also observed compared with two control scaffolds. After fluorescein diacetate staining, living cells with green fluorescence were evenly distributed on the scaffolds under the confocal laser microscope. (5) The alkaline phosphatase activity in cells seeded onto different scaffolds was ranked as follows: the PLGA/HA/BMP-2/0.25% chitosan scaffold > the PLGA/HA/BMP-2/0.5% chitosan scaffold > the PLGA/HA/BMP-2/1% chitosan scaffold > the PLGA/HA/BMP-2 scaffold > the PLGA/HA scaffold (P < 0.05). Taken together, the PLGA/HA/BMP-2/chitosan scaffold is suitable to release bioactive BMP-2 for stimulating cell adhesion, differentiation and proliferation, which is designed to optimize the tissue-engineered bone scaffold in bone tissue engineering strategies. And moreover, the optimal modification concentration of chitosan is 0.25%.
ABSTRACT
Background Trachoma is a common disease in ophthalmology,but few reports about the pathogenetic genotype are reported.Objective This study was to investigate the genotypes of Chlamydia trachomatis.Methods Conjunctival specimens were collected in 16 patients with trachoma in Beijing Tongren Eye Center from January,2003 and August,2006.Variable sequence 4 (VS4) of ompl fragment was amplified by nested PCR(n-PCR) using specific primer of Chlamydia trachomatis,and then the PCR products were sequenced.The DNA sequences were analyzed by software Clustal X and MEGA2,and the genetic characteristics were compared with the known sequences of GenBank.Results The PCR product fragment of MOMP gene of trachoma was 277 bp.Three types of Chlamydia trachomatis strains were idcntified in the 16 specimens,including B-genotype in 9 strains (56.3％),C-genotype in 4 strains(25.0％) and D-genotype in 3 strains(18.7％).High homology was seen in the gene sequences of Chlamydia trachomatis strains between the B-genotype or C-genotype strains and the same genotypes of GenBank or those from some districts of China.However,some differences were exhibited among the Dgenotype strains.Conclusions Identification of genotype of Chlamydia trachomatis has differential effect on trachoma and inclusion conjunctivitis.
ABSTRACT
<p><b>OBJECTIVE</b>To study the expression of RAS protein in human glioma tissues and its influence on tumor growth.</p><p><b>METHODS</b>RAS protein expression in glioma tissues was determined by immunohistochemical (IHC) staining. Subsequently, MTT cell proliferation assay, flow cytometry and Western blotting were used to assay U251 cells with reduced RAS expression.</p><p><b>RESULTS</b>The expression of RAS in glioma was increased and strongly correlated with pathological grade. Downregulation of RAS resulted in glioma cells growth suppression and increased apoptosis.</p><p><b>CONCLUSION</b>The expression level of RAS protein in human glioma was increased. Downregulation of RAS can inhibit glioblastoma cell growth through the RAS signal pathway.</p>
Subject(s)
Humans , Brain Neoplasms , Genetics , Metabolism , Pathology , Cell Growth Processes , Genetics , Cell Line, Tumor , Down-Regulation , Glioma , Genetics , Pathology , Immunohistochemistry , ras Proteins , GeneticsABSTRACT
The aqueous phase oxidation of gaseous elemental mercury (Hg(0)) by potassium persulfate (KPS) catalyzed by Ag(+) was investigated using a glass bubble column reactor. Concentration of gaseous mercury and potassium persulfate were measured by cold vapor atom absorption (CVAA) and ion chromatograph (IC), respectively. The effects of pH value, concentration of potassium persulfate and silver nitrate (SN), temperature, Hg(0) concentration in the reactor inlet and tertiary butanol (TBA), free radical scavenger, on the removal efficiency of Hg(0) were studied. The results showed that the removal efficiency of Hg(0) increased with increasing concentration of potassium persulfate and silver nitrate, while temperature and TBA were negatively effective. Furthermore, the removal efficiency of Hg(0) was much better in neutral solution than in both acidic and alkaline solution. But the influence of pH was almost eliminated by adding AgNO(3). High Hg(0) concentration has positive effect. The possible reaction mechanism of gaseous mercury was also discussed.