新生血管特异性结合肽GX1二聚体抑制胃癌新生血管生成的实验研究

目的:探讨新生血管特异性结合肽GX1二聚体对胃癌新生血管生成的影响。方法:化学合成GX1二聚体、GX1单体、对照肽二聚体，CCK-8实验、管状结构形成实验、迁移实验研究GX1二聚体对胃癌血管内皮细胞（co-HUVEC）增殖、微管形成、迁移能力的影响，流式细胞学技术分析其对细胞周期分布和凋亡的影响。结果:CCK-8结果显示，GX1二聚体与对照肽二聚体及PBS对照组相比，100~200 μmol/L可抑制co-HUVEC增殖，具有统计学差异（P<0.05），并呈剂量依赖性，GX1二聚体较单体抑制作用增强，并有统计学差异（P<0.05）。管状结构形成实验、细胞损伤迁移实验结果显示，与对照肽二聚体及对照组PBS 相比，GX1二聚体及GX1单体，均可抑制胃癌内皮细胞管状结构的形成及迁移，且二聚体抑制作用强于单体；对照肽二聚体仅有轻微的抑制胃癌内皮细胞管状结构的形成及迁移。流式细胞术分析显示，与对照肽二聚体及PBS对照组相比，GX1二聚体及GX1单体均可诱导细胞凋亡（P<0.05），且GX1二聚体的诱导作用强于GX1单体（P<0.05），而对细胞周期分布则无明显影响。结论:GX1二聚体和GX1单体均可抑制胃癌新生血管内皮细胞增殖、微管形成、迁移能力及诱导凋亡，且GX1二聚体较GX1单体作用增强。GX1二聚体有望代替单体成为胃癌新生血管靶向治疗小肽类药物。     

Diffusion of resin monomers through human carious dentin in vitro

Abstract The diffusion of 2-hydroxyethylmediacrylate (HEMA) and triethylene glycol dimethacrylate (TEGDMA) from light cured bonding resin-composite resin restorations through human carious dentin was investigated. Extracted human molar teeth with different degrees of caries were obtained from consenting donors. Teeth were classified into three groups according to caries severity (mild, moderate and severe) using subjective criteria. The outer carious lesions were then removed guided by a proprietary caries detector dye. Teeth with exposure of the pulp space after caries removal were excluded from the study. A polypropylene chamber was attached to the cemento-enamel junction of each tooth to contain 1 ml distilled water. Each cavity was restored with a HEMA containing bonding resin then a TEGDMA-containing resin composite. Water samples were retrieved over a lime course and analyzed by high performance liquid chromatography. There was great variation between teeth in HEMA and TEGDMA permeability. The cumulative amounts released were of similar magnitude to those observed in non-carious teeth for the mild and moderately-severe groups. However, the cumulative amounts released were markedly greater in severely carious teeth than in those with moderate or mild caries.     

Effects of storage time and temperature on the properties of two self-etching systems

OBJECTIVES: To evaluate the micro-shear bond strength to enamel and dentin, pH and hardness of two self-etching adhesives over a period of 60 weeks storage at different temperatures. MATERIALS AND METHODS: Two self-etching systems, an all-in-one adhesive, Clearfil Tri-S Bond (TS) and a two-step adhesive, Clearfil SE Bond (SE) were used in this study (both by Kuraray Medical, Osaka, Japan). Their micro-shear bond strengths to enamel and dentin were measured. The materials were then stored at 4, 23 or 37 degrees C. Their bond strengths were measured again after 1, 4, 16 and 60 weeks and compared to the base line. The nano-indentation hardness of the polymerized bonding, pH of SE primer and TS were also measured at the baseline and after 60 weeks of storage at three different temperatures. Bond-strength and hardness data were analyzed using ANOVA and post hoc tests at the significance level of 0.05. RESULTS: Two-way ANOVA analysis showed that both storage conditions and material type had significant effects on bond strength to enamel or dentin but the interactions of these factors were not significant for any of the substrates. One-way ANOVA post hoc tests revealed that the bond strength of adhesives stored at 37 degrees C significantly decreased during the storage period; with the earliest significant decreases observed at 4 weeks for TS and at 16 weeks for SE. After 60 weeks of storage, the hardness obtained for SE bonding resin was not significantly different with that at the baseline for 4, 23 and 37 degrees C groups, but there was a significant decrease observed in hardness for TS stored at 37 degrees C, compared to that at the baseline. The pH of both self-etching materials decreased when they were stored at 37 degrees C. CONCLUSION: Storage time and temperature significantly affected the bond strength of both materials through the time dependent hydrolysis and other changes that are likely to occur in the water-containing self-etching agents at high temperatures.     

Kinetic Investigations of Cu‐Mediated ATRP in Aqueous Solution

Cu‐mediated atom‐transfer radical polymerization (ATRP) is studied via on‐line vis/NIR spectroscopy in an aqueous solution of a monomer‐free model system, with CuBr/2,2′‐bipyridine acting as the catalyst, and 2‐hydroxyethyl 2‐bromoisobutyrate as the initiator, at a pressure of up to 2000 bar. Excess NaBr is added to avoid the water‐assisted dissociation of the Br–Cu(II)/L bond. The activation–deactivation equilibrium constant, K_model, is measured at different compositions of the water–poly(ethylene glycol) dimethylether (PEO) solvent mixture, in which PEO mimics a water‐soluble monomer. K_model increases by about three orders of magnitude in passing from a PEO to a water environment. The change in K_model is essentially due to the effect on the activation rate coefficient. Kinetic analysis of the model system upon variation of NaBr concentration in conjunction with predici simulations shows that the NaBr content has no significant impact on the activation and deactivation rate coefficients and thus on K_model, but on dispersity and on the degree of chain‐end functionality.

     

New Insight into the ATRP of Monovinyl and Divinyl Monomers

New insights are provided into the atom transfer radical polymerizations of styrene with 1,6‐bismaleimidohexane, tri‐ethylene glycol dimethacrylate (tri‐EGDMA), and divinyl benzene (DVB) as branching agents. Gas chromatography, proton nuclear magnetic resonance spectroscopy, and triple detection size exclusion chromatography are used to analyze the polymerizations and the polymers. The polymerizations and molecular weights of polymers differ because of the different levels of intramolecular cyclization and initiator efficiencies (IEs) among the three polymerization systems. High IE increases polymerization rate and restrains gelation, thereby facilitating preparation of branched polymers with high molecular weights. Polymers in the tri‐EGDMA system exhibit the lowest molecular weight and the broadest polydispersity because of some evident primary chain residues, whereas polymers in the DVB system show the highest molecular weight because of the low amount of the primary chain residues and high IE. The absence of branching monomer units in the primary chain residue of all these polymerizations is confirmed.

     

Fluorescent ROMP Monomers and Copolymers for Biomedical Applications

The synthesis and characterization of a series of green‐, blue‐, and red‐fluorescent exo‐oxanorbornene acid and imide monomers carrying nitrobenzofurazan, coumarin, and rhodamin B, respectively, as fluorophores are presented. These monomers carry oxanorbornene as polymerizable unit, and are readily copolymerized with bioactive functional oxanorbornene monomers by ring‐opening metathesis polymerization, as demonstrated by gel permeation chromatography and NMR spectroscopy. Due to the ease of synthesis of these monomers, and their cost‐effectiveness compared many to other fluorescent probes, they are useful for biomaterial applications.     

Visible Light Curable Restorative Composites for Dental Applications Based on Epoxy Monomer

A cationic photo-curable cycloaliphatic epoxy resin has been investigated as reactive monomer in blue light crosslinking process. We have demonstrated that camphorquinone is able to abstract labile hydrogen from the epoxy monomer, giving rise to the formation of carbon-centered radicals that are oxidized by the onium salt; a complete epoxy group conversion was reached after 50 s of irradiation. The presence of water up to 1 wt% was tolerated without any important detrimental effect on the kinetics of light-curing. The presence of the inorganic filler up to 65 wt% did not significantly influence the curing process.     

人参有效单体对活化的肾系膜细胞株的影响

目的:观察人参有效单体对活化的肾系膜细胞株的影响。方法:采用体外培养肾系膜细胞株的方法,将其分为空白对照组、TGF-β12ng/ml组、TGF-β12ng/ml+中药10-5g/ml组和TGF-β12ng/ml+中药10-6g/ml组。采用MTT法观察24h中药单体对系膜细胞株的作用以及ELISA法对TGF-β的分泌情况。结果:与空白对照组相比,加入TGF-β1刺激因子可以促进系膜细胞株的活化(P<0.05),以及TGF-β的分泌(P<0.01),中药单体可以抑制活化的细胞株增殖和TGF-β的分泌(P<0.05或P<0.01)。结论:人参中药单体可以抑制活化的肾系膜细胞株的增殖,有效防治肾纤维化,其可能的作用机制与其抑制TGF-β的分泌有关。     

Parkinson disease-associated mutation R1441H in LRRK2 prolongs the “active state” of its GTPase domain

Mutation in leucine-rich-repeat kinase 2 (LRRK2) is a common cause of Parkinson disease (PD). A disease-causing point mutation R1441H/G/C in the GTPase domain of LRRK2 leads to overactivation of its kinase domain. However, the mechanism by which this mutation alters the normal function of its GTPase domain [Ras of complex proteins (Roc)] remains unclear. Here, we report the effects of R1441H mutation (Roc_R1441H) on the structure and activity of Roc. We show that Roc forms a stable monomeric conformation in solution that is catalytically active, thus demonstrating that LRRK2 is a bona fide self-contained GTPase. We further show that the R1441H mutation causes a twofold reduction in GTPase activity without affecting the structure, thermal stability, and GDP-binding affinity of Roc. However, the mutation causes a twofold increase in GTP-binding affinity of Roc, thus suggesting that the PD-causing mutation R1441H traps Roc in a more persistently activated state by increasing its affinity for GTP and, at the same time, compromising its GTP hydrolysis.Mutation in leucine-rich-repeat kinase 2 (LRRK2) is a common cause of Parkinson disease (PD) (1–5). LRRK2 is a large (2,527-aa) multidomain protein consisting of seven putative domains (2), including a Ras-like GTPase domain called Ras of complex proteins (Roc), followed by a domain called C-terminal of Roc (COR), which is then followed by a kinase domain (Kin). It remains unclear how perturbations of these activities result in disease; however, the most common mutation in LRRK2-associated PD, G2019S in the kinase domain, shows higher kinase activity than wild type; therefore, its overactivation might be associated with disease pathogenesis (6).The tandem Roc-COR-Kin arrangement suggests that their activities might be coupled such that the GTPase activity of Roc might modulate the kinase activity. Indeed, several studies have shown that GTP binding to the Roc domain regulates the activity of the Kin domain (7, 8). Moreover, a PD-associated mutation in the Roc domain (R1441C) has been shown to have higher kinase activity (9), thus suggesting that mutations in the Roc domain, also up-regulate kinase activity.Understanding the function of Roc and its mechanism of action is important for understanding the mechanism of PD pathogenesis and therapeutic development. However, because of the lack sufficient quantity of protein samples amendable for detailed investigations, the biochemical properties and enzymatic activities of the Roc domain of LRRK2 are poorly understood.Here, we describe a stably folded construct of human Roc domain that enabled us to investigate quantitatively its biochemical and enzymatic properties. The results revealed that a PD-causing mutation R1441H in the Roc domain renders it less active at hydrolyzing GTP, as well as having higher affinity for GTP, than its wild-type counterpart, thereby increasing the residence time of its GTP-bound “active state,” which is associated with PD pathogenesis (8).