视黄酸和亚硒酸钠对肝癌细胞某些表型逆转的加和作用

 人肝癌细胞株SMMC-7721经1μmol/L视黄酸和或2.5μmol/L亚硒酸钠处理后,膜上纤维连接蛋白沉着量逐日上升,且较相应天数的对照组细胞增加,而甲胎蛋白分泌量和~3H-TdR参入率被明显抑制。视黄酸和亚硒酸钠同时处理的联合组作用强度接近于两者单独使用时作用强度的加和。对以上结果和视黄酸及亚硒酸钠使肝癌细胞接触抑制恢复及表型逆转的关系作了讨论。     

Primitive streak-forming cells of the chick invaginate through a basement membrane

Summary Recently fibronectin was shown to appear in the development of the chick for the first time as a thin band on the epiblastic side facing the hypoblast just prior to primitive streak formation. It was thus suggested that fibronectin might be instrumental in the migration of cells that lead to axis formation during primitive streak formation. In the present work we have examined simultaneously for the presence of fibronectin and the specific basement membrane glycoprotein laminin during primitive streak formation using immunofluorescence methods. Laminin was found to be expressed between the epiblast and the hypoblast of stage XIII¹ chick blastoderms. During the immediately following process of streak formation the laminin was found to be continuously detectable throughout the area covered by the hypoblast, but disrupted on the streak area. Fibronectin was found to co-distribute with laminin in stage XIII and in the early primitive streak chick blastoderms. It is concluded that at stage XIII laminin and fibronectin form part of a basement membrane that is partially disrupted during the immediately following process of primitive streak formation in order to allow the migration of the streak-forming epiblastic cells during this morphogenetic process.     

A polarized light and electron microscopic study of the birefringent fibrils inPhysarum plasmodia

Summary The birefringent fibrils in thin-spread plasmodium ofPhysarum polycephalum have been investigated with both polarizing and electron microscopes. The birefringent fibrils were classified into three groups by polarized light microscopy. The first type of fibril is observed in the advancing frontal region as a mutual orthogonal array. The birefringence changes rhythmically in accordance with the shuttle streaming. The second type of birefringent fibril is located in the strand region and runs parallel or somewhat oblique to the strand axis. The third type is observed in the strand region always perpendicular to the streaming axis. Electron microscopy confirmed that all these fibrils are composed of microfilaments, which range in densities in the cross view of the fibril from 1.2 to 1.7 × 10³/m² (1.5 × 10³/(xm² on the average).     

Effect of supraoptimal temperatures on the function of the subcortical fibrils and an endoplasmic factor inNitella internodes

Summary The effect of supraoptimal temperatures onNitella cells was studied with special reference to the function of subcortical fibrils and an endoplasmic factor. Local heat-treatment (50 °C for 1 minute) of an internodal cell ofNitella disclosed that 1. the subcortical fibrils in the treated area remain normal, not affected by the treatment, 2. the subcortical fibrils alone produce no cytoplasmic streaming, 3. the endoplasm contains an extremely heat-labile factor which is indispensable for streaming, and 4. the stagnant endoplasm in the heat-treated area is neither coagulated nor gelated by heat.Preliminary reports appeared in Proc. 37th Annu. Meet. Bot. Soc. Jpn. P. 160 (1972, in Japanese) and in Abst. Annu. Meet. Jpn. Soc. Cell Biol. p. 57 (1975, in Japanese).     

Characterization of the cytoplasmic fibrils of Treponema refringens (Nichols)

The cytoplasmic fibrils of Treponema refringens were studied in situ by electron microscopy of thin sectioned and negatively stained cells. From 5 to 21 parallel fibrils ran through the cell in a band adjacent to the inner side of the cytoplasmic membrane, on the inner sides of the curves of the spirochete. The nuclear areas of cells were adjacent to the fibrils. Cross sections of fibrils isolated from cells which had been lysed were polygonal and not uniformly electron dense. Polyacrylamide gel electrophoresis of partially purified fibril preparations indicated their main component to be a protein with a molecular weight of 97,000. Fibrils were solubilized by 1% trypsin, 1% pronase, 6 M urea, 1 N HCl, 0.005 N NaOH or 1.3% sodium dodecyl sulfate. By electron microscopy of negatively stained isolated fibrils, each fibril was found to be a complex arrangement of strands rather than a single tubule.Abbreviations CM Cytoplasmic membrane - PTA Phosphotungstic acid - UOx Uranyl oxalate - SDS sodium dodecyl sulfate This communication is Journal Acticle No. 7644 from the Michigan Agricultural Experiment Station     

Aggregation inAzospirillum brasilense Cd: Conditions and factors involved in cell-to-cell adhesion

Aggregation of the root-inhabiting, asymbiotic N-fixingAzospirillum brasilense Cd (ATCC-29729), was studied. Aggregation occurred towards the end of the exponential phase and during the stationary phase. More aggregates were formed in media supplemented with organic acids than in those containing sugars as a sole carbon source. Maximum growth with no aggregation was obtained in a medium containing both fructose and malate as carbon sources. Aggregation was increased by poly-L-lysine and carbodiimide as well as by increasing the C/N ratio and decreasing combined nitrogen in the growth medium. Aggregates were stable at pH levels of >8 and <6, but dispersed at pH 7.1. Treatment of Azospirillum with NaEDTA resulted in loss of both aggregative capacity and the ability of adsorb to wheat roots without losing cell viability. When extracted bacteria were suspended in their dialysed NaEDTA extract, both their aggregative and adsorptive capacities were restored.The dialysed NaEDTA extract agglutinated bacterial cells and red blood cells, especially of type O. When the extract was run through a sepharose gel, it separated into three main fractions, of which only one showed agglutinating capacity. Gel electrophoresis of this fraction revealed a single band (MW 97,000) which reacted positively to Schiff's reagent and Coomassie brilliant blue R-250, typical to a glycoprotein. Bacterial agglutination by this fraction was strongly inhibited by D-glucose, melibiose and -metyl glucoside. No evidence as to the involvement of cellulose fibrils in aggregation was found. It is suggested that glycoprotein(s) and glucose residues located on the outer surface of the cells are involved in aggregation of Azospirillum.     

猪链球菌2型FBPS的纤连蛋白结合部位的初步确定

根据猪链球菌2型江苏分离株HA9801的fbps基因序列,设计合成不同的引物,用含全长fbps的pMD-T-FBPS质粒为模板,通过PCR技术,扩增不同片段fbps,并按正确的阅读框架定向克隆到表达载体pET-32a( ),构建分别表达全长7~82、7~165和87~320氨基酸FBPS的重组表达质粒pFBPS、pFBPS(7~82)、pFBPS(7~165)和pFBPS(87~320);将重组质粒转化大肠杆菌BL21(DE)株,经IPTG诱导,表达rFBPS(7~82)、rFBPS(7~165)、rFBPS(87~320)和rFBPS(全长),分子量分别为29、34、42及83kD的融合蛋白。配基亲和Western blot试验表明,表达的融合蛋白除rFBPS(7~82)外,均可与人纤连蛋白(Fn)结合,由此可以推断SS2的纤连蛋白/血纤蛋白原结合蛋白(FBPS)N端87~165氨基酸区域为具有结合活性的线性部位。     

精液源性病毒感染增强因子SEVI-HIV性传播中的重要因素

精液源性病毒增强因子(Semen-derived enhancer of viral infection,SEVI)是前列腺酸性磷酸酶(Prostatic acidphosphatase,PAP)位于PAP248-286的多肽片段,可增强人免疫缺陷病毒(Human immunodeficiency virus,HIV)的感染性。SEVI促进HIV感染的作用机制包括:①富含阳离子氨基酸残基的SEVI能通过静电作用降低HIV病毒颗粒与靶细胞之间的静电排斥;②SEVI在人体液中呈无序状态,利于病毒与靶细胞膜相互作用;③SEVI直接捕获HIV颗粒,提高病毒在靶细胞表面沉降速度,促进病毒与靶细胞的吸附和融合。目前已发现能抑制SEVI活性的物质包括:绿茶来源的EGCG(没食子儿茶素没食子酸酯)、氨基喹啉类小分子化合物Surfen、ThT类似物BTA-EG6等,能通过阻断HIV与SEVI结合或阻止其淀粉样纤维的形成,降低SEVI的病毒感染增强作用。研究SEVI的生物学特性及作用机制对防治HIV感染具有较为重要的指导意义。     

Ail protein binds ninth type III fibronectin repeat (9FNIII) within central 120-kDa region of fibronectin to facilitate cell binding by Yersinia pestis

The Yersinia pestis adhesin molecule Ail interacts with the extracellular matrix protein fibronectin (Fn) on host cells to facilitate efficient delivery of cytotoxic Yop proteins, a process essential for plague virulence. A number of bacterial pathogens are known to bind to the N-terminal region of Fn, comprising type I Fn (FNI) repeats. Using proteolytically generated Fn fragments and purified recombinant Fn fragments, we demonstrated that Ail binds the centrally located 120-kDa fragment containing type III Fn (FNIII) repeats. A panel of monoclonal antibodies (mAbs) that recognize specific epitopes within the 120-kDa fragment demonstrated that mAb binding to (9)FNIII blocks Ail-mediated bacterial binding to Fn. Epitopes of three mAbs that blocked Ail binding to Fn were mapped to a similar face of (9)FNIII. Antibodies directed against (9)FNIII also inhibited Ail-dependent cell binding activity, thus demonstrating the biological relevance of this Ail binding region on Fn. Bacteria expressing Ail on their surface could also bind a minimal fragment of Fn containing repeats (9-10)FNIII, and this binding was blocked by a mAb specific for (9)FNIII. These data demonstrate that Ail binds to (9)FNIII of Fn and presents Fn to host cells to facilitate cell binding and delivery of Yops (cytotoxins of Y. pestis), a novel interaction, distinct from other bacterial Fn-binding proteins.     

Surface functionalization of inorganic nano-crystals with fibronectin and E-cadherin chimera synergistically accelerates trans-gene delivery into embryonic stem cells

Stem cells holding great promises in regenerative medicine have the potential to be differentiated to a specific cell type through genetic manipulation. However, conventional ways of gene transfer to such progenitor cells suffer from a number of disadvantages particularly involving safety and efficacy issues. Here, we report on the development of a bio-functionalized inorganic nano-carrier of DNA by embedding fibronectin and E-cadherin chimera on the carrier, leading to its high affinity interactions with embryonic stem cell surface and accelerated trans-gene delivery for subsequent expression. While only apatite nano-particles were very inefficient in transfecting embryonic stem cells, fibronectin-anchored particles and to a more significant extent, fibronectin and E-cadherin-Fc-associated particles dramatically enhanced trans-gene delivery with a value notably higher than that of commercially available lipofection system. The involvement of both cell surface integrin and E-cadherin in mediating intracellular localization of the hybrid carrier was verified by blocking integrin binding site with excess free fibronectin and up-regulating both integrin and E-cadherin through PKC activation. Thus, the new establishment of a bio-functional hybrid gene-carrier would promote and facilitate development of stem cell-based therapy in regenerative medicine.