The affinity ratio--its pivotal role in gold nanoparticle-based competitive colorimetric aptasensor

We present an important role of the ratio of affinities in unmodified gold nanoparticles-based colorimetric aptasensor reactions. An affinity ratio, representing the competitive interactions among aptamers, targets, and unmodified gold nanoparticles (umAuNPs), was found to be an important factor for the sensitivity (the performance), where the affinity ratio is the affinity of the aptamer to targets divided by the affinity to umAuNPs (K(dAuNP)/K(dTarget)). In this study, the five different aptamers having different affinity ratios to both umAuNPs and targets are used, and the degree of color change is well correlated with its affinity ratio. This result is verified by using a tetracycline binding aptamer (TBA) showing different affinities to its three derivatives, tetracycline, oxytetracycline and doxycycline. Based on this model, the sensitivity of umAuNPs based colorimetric detection for ibuprofen can be enhanced simply through reducing the ibuprofen binding aptamer's affinity to umAuNP by using bis (p-sulfonatophenyl) phenylphosphine as an AuNP-capping ligand, instead of using the citrate. As a result, a clear color change is observed even at a 20-fold less amount of ibuprofen. This study presents that the performance (detection sensitivity) of umAuNPs-based colorimetric aptasensors could be improved by simply adjusting the affinity ratio of the aptamers to targets and umAuNPs, without knowing the conformational changes of aptamers upon the target binding or needing any modification of aptamer sequences.     

The E-cadherin (CDH1) -160C>A polymorphism associated with gastric cancer among Asians but not Europeans

E-cadherin (CDH1) is a tumor suppressor gene involved in epithelial cell-cell interactions and plays important roles in the etiology of gastric cancer. Studies reporting conflicting results on the role of -160C>A polymorphism in the CDH1 promoter region on gastric cancer risk led us to perform a meta-analysis to investigate this relationship. Thirteen published case-control studies including 2509 gastric cancer cases and 3687 controls were identified. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of the association. Overall, individuals with the variant genotypes were not associated with a significant gastric cancer risk (AA vs. CC: OR?=?1.04, 95% CI: 0.74-1.48; CA vs. CC: 1.02, 0.85-1.21; AA/CA vs. CC: 1.03, 0.86-1.22; AA vs. CA/CC: 1.03, 0.74-1.43). However, in the stratified analysis by ethnicity, significantly decreased gastric cancer risk was found among Asians in dominant model (AA/CA vs. CC: 0.84, 0.72-0.99). Further, when stratified by clinicopathologic characteristics of gastric cancer, no statistically significant result was observed for any analysis. The results suggested that the CDH1 -160C>A polymorphism may contribute to susceptibility to gastric cancer among Asians. Additional well-designed large studies will be required to validate this association in different populations.     

Activity of the RhoU/Wrch1 GTPase is critical for cranial neural crest cell migration

The neural crest (NC) is a stem cell-like population that arises at the border of neural and non-neural ectoderm. During development, NC undergoes an epithelio-mesenchymal transition (EMT), i.e. loss of epithelial junctions and acquisition of pro-migratory properties, invades the entire embryo and differentiates into a wide diversity of terminal tissues. We have studied the implication of Rho pathways in NC development and previously showed that RhoV is required for cranial neural crest (CNC) cell specification. We show here that the non-canonical Wnt response rhoU/wrch1 gene, closely related to rhoV, is also expressed in CNC cells but at later stages. Using both gain- and loss-of-function experiments, we demonstrate that the level of RhoU expression is critical for CNC cell migration and subsequent differentiation into craniofacial cartilages. In in vitro cultures, RhoU activates pathways that cooperate with PAK1 and Rac1 in epithelial adhesion, cell spreading and directional cell migration. These data support the conclusion that RhoU is an essential regulator of CNC cell migration.     

Vascular endothelial growth factor signals endothelial cell production of nitric oxide and prostacyclin through flk-1/KDR activation of c-Src.

Vascular endothelial growth factor (VEGF) is a potent endothelial cell-specific mitogen that promotes angiogenesis, vascular hyperpermeability, and vasodilation by autocrine mechanisms involving nitric oxide (NO) and prostacyclin (PGI(2)) production. These experiments used immunoprecipitation and immunoassay procedures to characterize the signaling pathways by which VEGF induces NO and PGI(2) formation in cultured endothelial cells. The data showed that VEGF stimulates complex formation of the flk-1/kinase-insert domain-containing receptor (KDR) VEGF receptor with c-Src and that Src activation is required for VEGF induction of phospholipase C gamma1 activation and inositol 1,4,5-trisphosphate formation. Reporter cell assays showed that VEGF promotes a approximately 50-fold increase in NO formation, which peaks at 5-20 min. This effect is mediated by a signaling cascade initiated by flk-1/KDR activation of c-Src, leading to phospholipase C gamma1 activation, inositol 1,4,5-trisphosphate formation, release of [Ca(2+)](i) and nitric oxide synthase activation. Immunoassays of VEGF-induced 6-keto prostaglandin F(1alpha) formation as an indicator of PGI(2) production revealed a 3-4-fold increase that peaked at 45-60 min. The PGI(2) signaling pathway follows the NO pathway through release of [Ca(2+)](i), but diverges prior to NOS activation and also requires activation of mitogen-activated protein kinase. These results suggest that NO and PGI(2) function in parallel in mediating the effects of VEGF.     

黄连属(毛茛科)花的形态发生

本文运用扫锚电子显微镜（SEM）观察了黄连属（Coptis）植物花的形态发生和发育过程,结果表明,该属植物所有的花部器官均为螺旋状发生,雄蕊为向心式发育,花瓣原基有微弱的延迟发育,心皮原基为对折型（即马蹄形）,子房为半封闭类型,子房柄是在发育过程中形成的。通过与其它具T．型染色体类群在花形态发生上的比较,认为黄连属表现出了某些原始的性状,这一结果与分子系统学研究认为黄连属为毛莨科的基部类群的结论一致。