气生凤梨叶片结构研究

我们以地生凤梨(Guzmnania‘Denise’)作为对照,利用扫描电镜技术、石蜡切片技术对3种气生凤梨(Til-landsia stricta‘Hard leaf’、T.stricta‘Cotton candy’与T.filifolia)的叶片表面和内部结构进行了研究。结果表明所有凤梨叶片表面均分布着葵花状的鳞片,鳞片由碟状细胞、环状细胞和翼状细胞3类细胞构成,最内部的碟状细胞通过柄状细胞与叶片内部的叶肉细胞相连。气生凤梨叶片表面鳞片白色、蜡质、密度很大,但气孔很少或不可见,暗示鳞片除吸收水分和养分外,还可能具有减少光呼吸、排水及反射阳光等功能。另外,不同的气生凤梨之间叶片表面鳞片的形态、大小和密度也不同,反映了它们对其不同起源地及现生存环境的适应。     

艾氏腹水瘤耐药瘤细胞的表面电荷和浸润

细胞电泳法测知细胞表面带有电荷,结合化学或酶学方法证明:表面电荷是由带负电荷的羧基、磷酸等基团和带正电荷的氨基、硫氢基等基团组成的。不同种的细胞或不同状态下的同一种细胞,它们的表面电荷密度是不同的。细胞表面电荷密度的改变可能与细胞表面的某些行为有关。例如,去掉带有羧基的神经氨酸,细胞的十多种功能发生改变(Winzler,1970)。这固然可能反映细胞表面的神经氨酸具有多种功能,亦说明对表面电荷的生物学功能尚不够了解。我们曾看到艾氏腹水瘤细胞获得耐药性后,细胞表面的电荷密度发生改变,而且,这种改变并不随耐药性的消失而恢复(顾国彦和刘黎,1965)。本     

几种植物生殖细胞质膜表面的凝集素受体荧光标记

为进一步探讨从生殖细胞到精子的发育过程中细胞质膜表面凝集素受体的可能变化,及其与两类对凝集素标记有不同结果的精子的关系,用异硫氰酸荧光素标记的伴刀豆凝集素(Con A)、麦芽凝集素(WGA)和大豆凝集素(SBA)对蚕豆(Vicia faba L.)、鸢尾(Iris tectorium Maxim.)和朱顶红(Hippeastrum vittatum Herb.)的生殖细胞质膜表面的凝集素受体进行标记.结果显示:在不同植物中均有部分生殖细胞不能被凝集素探针标记,且在保持尾状形态的生殖细胞的表面发现有凝集素受体的极性分布.这可能是导致部分精子表面不能被同种凝集素标记的重要原因.此外,同一种凝集素受体在不同物种的生殖细胞上分布不一致,不同的凝集素受体在同一种植物的生殖细胞上的分布模式亦有不同.在蚕豆和鸢尾的生殖细胞表面均有这三种凝集素的受体.在朱顶红生殖细胞的表面有前两种凝集素的受体,分布比较均一,但是没有大豆凝集素的受体.此外,在具尾生殖细胞表面发现有凝集素受体极性分布的现象,为探讨精细胞功能及其表面糖蛋白分布的可能差异提供了重要启示.     

巴氏碳球C_(60)对体外培养HeLa细胞的光敏杀伤效应

采用MTT比色分析法,观察了不同C_(60)浓度和不同光照强度下C_(60)对体外培养的HeLa细胞的光敏杀伤效应。结果表明,C_(60)在30μg/ml,光强4000Lux的条件下即可杀伤大部分细胞。受伤细胞圆缩、脱壁,里面颗粒增多,失去表面微绒毛状结构。当光强增大时,细胞表面甚至出现破损。     

ABC法在膜受体流动性测量中的应用

本文首次把ABC法应用于受体流动性测量中的膜表面受体荧光标记,利用FRAP(Fluorescence Recovery After Photobleaching)技术实现了细胞内吞过程中膜受体流动性变化的测量.实验用Con A—Biotin和Avidin—FITC(ABC法)标记巨噬细胞ConA受体,测量ConA刺激不同时间细胞膜表面受体的荧光强度、扩散系数和荧光恢复率的变化.结果显示ABC标记法适合于测量细胞内吞过程中膜表面受体的流动性变化,且具有较高的灵敏度高;巨噬细胞受ConA刺激后,膜表面ConA受体的扩散系数和荧光恢复率较静息状态时明显降低.     

67kD层粘连蛋白受体的克隆、表达及其对肝癌细胞侵袭能力的影响

探讨细胞膜表面 6 7kD层粘连蛋白受体 (6 7kDlamininreceptor ,6 7LR)在肝癌细胞侵袭转移中的作用 ,从肝癌细胞中提取RNA ,通过RT PCR扩增 6 7LR的前体——— 37kD层粘连蛋白受体前体(37kDlamininreceptorprecursor,37LRP)基因并定向克隆到真核表达载体pcDNA3.1 myc His(- )A ,采用脂质体将重组质粒转染到HepG2肝癌细胞中 ,通过G4 1 8筛选和RT PCR、流式细胞术鉴定 ,获得了细胞膜表面 6 7LR高表达 (阳性率为 6 9.2 % )和低表达 (阳性率为 1 1 .7% )的细胞克隆 ,采用体外细胞侵袭实验测定不同细胞的侵袭能力 ,发现膜表面 6 7LR高表达的细胞侵袭能力明显高于低表达及不表达细胞 ,说明 6 7LR在肝癌细胞侵袭转移过程中可能具有重要意义     

细胞表面糖链末端唾液酸和岩藻糖与某些细胞生物学行为的关系

用神经氨酸酶和a-L-岩藻糖苷酶分别切除人肝癌细胞株7721细胞表面糖链中的末端唾液酸(SA)和岩藻糖(Fuc)残基来研究表面聚糖结构和某些细胞生物学行为之间的关系.选择细胞对纤连蛋白(Fn)、层黏蛋白(Ln)和人脐静脉内皮细胞(HUVEC)的黏附能力、细胞趋化性迁移以及趋化性侵袭作为细胞行为的指标.结果表明表面糖链末端SA对细胞黏附至Fn并不必需,对细胞黏附至Ln和细胞的趋化性侵袭却至为重要,而对细胞黏附至HUVEC以及趋化性迁移则为关键性残基.与SA相比,Fuc可能参与细胞Fn、Ln和HUVEC的黏附,但对趋化性迁移以及趋化性侵袭并不重要.细胞对HUVEC的黏附以及趋化性迁移和侵袭可被唾液酸化Lewis X(SLex)的单抗抑制,但不被未唾液酸化的Lewis X(Lex)单抗抑制,这一结果支持SA在上述三种细胞过程中较Fuc残基重要.     

不同组织来源的细胞建立诱导多能干细胞系的研究

目的:比较不同组织来源的细胞生成iPS细胞的效率,获得高效制备iPS细胞的组织类型.方法:通过四种逆转录病毒(OCT4/SOX2/KLF4/c-MYC)转染羊水细胞、绒毛细胞和皮肤成纤维细胞,建立不同组织来源的iPS细胞系.结果:我们建立了羊水、绒毛细胞和皮肤细胞三个不同组织来源的iPS细胞系,并对其多能性基因Oct4、Nanog以及分子表面标记Tra-1.60以及体外分化为三个胚层能力进行鉴定,发现利用羊水细胞建立iPS细胞的效率显著高于绒毛细胞和皮肤细胞.结论:羊水细胞可能是制备iPS细胞的理想细胞类型.     

盐度胁迫对尼罗罗非鱼鳃氯细胞调节变化的影响

采用扫描电镜和免疫组化技术,研究了尼罗罗非鱼(Oreochromis niloticus)鳃中氯细胞的分布,及其不同盐度(0、10、20、30)胁迫对氯细胞数目和形态变化的影响.扫描电镜结果表明:氯细胞分布在鳃丝的鳃小片基部,根据其表面开口长度,可分为Ⅰ型(＞6.5μm)、Ⅱ型(3.2～6.5μm)和Ⅲ型(＜3.2 μm)3种亚型;不同盐度下氯细胞总数目变化趋势为盐度10＜盐度20＜盐度0＜盐度30;从盐度0转移到盐度10后,氯细胞总数目减少,主要是由于Ⅰ型氯细胞数目显著下降;盐度20中的氯细胞数量高于盐度10,但不显著;盐度30中的氯细胞数量随Ⅲ型氯细胞数量的提高而显著增加.免疫组织化学进一步证实了不同盐度条件下Na+-K+-ATPase免疫反应性细胞均分布在鳃丝的鳃小片基部.本研究结果表明,尼罗罗非鱼可通过改变鳃氯细胞数量和形态结构来适应环境中的盐度变化,推测Ⅰ型氯细胞和Ⅲ型氯细胞分别在低盐、高盐适应中起着重要作用.     

EWI-2wint分子与丙型肝炎病毒感染

丙型肝炎病毒(hepatitis C virus,HCV)的感染具有严格的种属特异性和组织特异性,其建立感染的第1步是病毒颗粒通过宿主细胞表面的分子黏多糖分子(glycosaminoglycans,GAG)及低密度脂蛋白受体(low-density lipoprotein receptor,LDLr)等黏附在细胞表面,然后依次与细胞表面的B类Ⅰ型清道夫受体(scavenger receptor B type Ⅰ,SR-B Ⅰ)、CD81、紧密连接蛋白Claudin-1等受体分子结合,再经网格蛋白、脂筏等介导的细胞内吞、融合,完成病毒的细胞入侵过程.     

Arrangement of type IV collagen on NH2 and COOH functionalized surfaces

Apart from the paradigm that cell–biomaterials interaction depends on the adsorption of soluble adhesive proteins we anticipate that upon distinct conditions also other, less soluble ECM proteins such as collagens, associate with the biomaterials interface with consequences for cellular response that might be of significant bioengineering interest. Using atomic force microscopy (AFM) we seek to follow the nanoscale behavior of adsorbed type IV collagen (Col IV)—a unique multifunctional matrix protein involved in the organization of basement membranes (BMs) including vascular ones. We have previously shown that substratum wettability significantly affects Col IV adsorption pattern, and in turn alters endothelial cells interaction. Here we introduce two new model surfaces based on self‐assembled monolayers (SAMs), a positively charged –NH₂, and negatively charged –COOH surface, to learn more about their particular effect on Col IV behavior. AFM studies revealed distinct pattern of Col IV assembly onto the two SAMs resembling different aspects of network‐like structure or aggregates (suggesting altered protein conformation). Moreover, the amount of adsorbed FITC‐labeled Col IV was quantified and showed about twice more protein on NH₂ substrata. Human umbilical vein endothelial cells attached less efficiently to Col IV adsorbed on negatively charged COOH surface judged by altered cell spreading, focal adhesions formation, and actin cytoskeleton development. Immunofluorescence studies also revealed better Col IV recognition by both α₁ and α₂ integrins on positively charged NH₂ substrata resulting in higher phosphorylated focal adhesion kinase recruitment in the focal adhesion complexes. On COOH surface, no integrin clustering was observed. Taken altogether these results, point to the possibility that combined NH₂ and Col IV functionalization may support endothelization of cardiovascular implants. Biotechnol. Bioeng. 2011;108: 3009–3018. © 2011 Wiley Periodicals, Inc.     

Use of Self-Assembled Monolayers of Different Wettabilities To Study Surface Selection and Primary Adhesion Processes of Green Algal (Enteromorpha) Zoospores

We investigated surface selection and adhesion of motile zoospores of a green, macrofouling alga (Enteromorpha) to self-assembled monolayers (SAMs) having a range of wettabilities. The SAMs were formed from alkyl thiols terminated with methyl (CH₃) or hydroxyl (OH) groups or mixtures of CH₃- and OH-terminated alkyl thiols and were characterized by measuring the advancing contact angles and by X-ray photoelectron spectroscopy. There was a positive correlation between the number of spores that attached to the SAMs and increasing contact angle (hydrophobicity). Moreover, the sizes of the spore groups (adjacent spores touching) were larger on the hydrophobic SAMs. Video microscopy of a patterned arrangement of SAMs showed that more zoospores were engaged in swimming and “searching” above the hydrophobic sectors than above the hydrophilic sectors, suggesting that the cells were able to “sense” that the hydrophobic surfaces were more favorable for settlement. The results are discussed in relation to the attachment of microorganisms to substrata having different wettabilities.     

Role of surface chemistry in protein remodeling at the cell-material interface

Background

The cell-material interaction is a complex bi-directional and dynamic process that mimics to a certain extent the natural interactions of cells with the extracellular matrix. Cells tend to adhere and rearrange adsorbed extracellular matrix (ECM) proteins on the material surface in a fibril-like pattern. Afterwards, the ECM undergoes proteolytic degradation, which is a mechanism for the removal of the excess ECM usually approximated with remodeling. ECM remodeling is a dynamic process that consists of two opposite events: assembly and degradation.

Methodology/Principal Findings

This work investigates matrix protein dynamics on mixed self-assembled monolayers (SAMs) of –OH and –CH₃ terminated alkanethiols. SAMs assembled on gold are highly ordered organic surfaces able to provide different chemical functionalities and well-controlled surface properties. Fibronectin (FN) was adsorbed on the different surfaces and quantified in terms of the adsorbed surface density, distribution and conformation. Initial cell adhesion and signaling on FN-coated SAMs were characterized via the formation of focal adhesions, integrin expression and phosphorylation of FAKs. Afterwards, the reorganization and secretion of FN was assessed. Finally, matrix degradation was followed via the expression of matrix metalloproteinases MMP2 and MMP9 and correlated with Runx2 levels. We show that matrix degradation at the cell material interface depends on surface chemistry in MMP-dependent way.

Conclusions/Significance

This work provides a broad overview of matrix remodeling at the cell-material interface, establishing correlations between surface chemistry, FN adsorption, cell adhesion and signaling, matrix reorganization and degradation. The reported findings improve our understanding of the role of surface chemistry as a key parameter in the design of new biomaterials. It demonstrates the ability of surface chemistry to direct proteolytic routes at the cell-material interface, which gains a distinct bioengineering interest as a new tool to trigger matrix degradation in different biomedical applications.     

Effects of surface charge and Gibbs surface energy on the settlement behaviour of barnacle cyprids (Balanus amphitrite)

Gibbs surface energy has long been considered to be an important parameter in the design of fouling-resistant surfaces for marine applications. Rigorous testing of the hypothesis that settlement is related to Gibbs surface energy however has never been accomplished, due mainly to practical limitations imposed by the necessary combination of surface engineering and biological evaluation methods. In this article, the effects of surface charge and Gibbs surface energy on the settlement of cyprids of an important fouling barnacle, Balanus amphitrite, were evaluated. Settlement assays were conducted on a range of self-assembled monolayers (SAMs) (CH₃-, OH-, COOH-, N(CH₃)₃ ⁺-, NH₂-terminated), presented in gold-coated polystyrene well plates, varying in terms of their surface charge and Gibbs surface energy. Contrary to contemporary theory, settlement was not increased by high-energy surfaces, rather the opposite was found to be the case with cyprids settling in greater numbers on a low-energy CH₃- SAM compared to a high-energy OH- SAM. Settlement was also greater on negatively-charged SAMs, compared to neutral and positively-charged SAMs. These findings are discussed in the context of data drawn from surfaces that varied in multiple characteristics simultaneously, as have been used previously for such experiments. The finding that surface charge, rather than total surface energy, may be responsible for surface selection by cyprids, will have significant implications for the design of future fouling-resistant materials.     

The responses of osteoblasts to fluid shear stress depend on substrate chemistries

Natural bone tissue receives chemical and mechanical stimuli in physiological environment. The effects of material chemistry alone and mechanical stimuli alone on osteoblasts have been widely investigated. This study reports the synergistic influences of material chemistry and flow shear stress (FSS) on biological functions of osteoblasts. Self-assembled monolayers (SAMs) on glass slides with functional groups of OH, CH₃, and NH₂ were employed to provide various material chemistries, while FSS (12 dynes/cm²) was produced by a parallel-plate fluid flow system. Material chemistry alone had no obvious effects on the expressions of ATP, nitric oxide (NO), and prostaglandin E₂ (PGE₂), whereas FSS stimuli alone increased the production of those items. When both material chemistry and FSS were loaded, cell proliferation and the expressions of ATP, NO and PGE₂ were highly dependent on the material chemistry. Examination of the focal adhesion (FA) formation and F-actin organization of osteoblasts before FSS exposure indicates that the FA formation and F-actin organization followed similar chemistry-dependence. The inhibition of FAs and/or disruption of F-actins eliminated the material dependence of FSS-induced ATP, PGE₂ and NO release. A possible mechanism is proposed: material chemistry controls the F-actin organization and FA formation of osteoblasts, which further modulates FSS-induced cellular responses.     

The leucine rich amelogenin protein (LRAP) adsorbs as monomers or dimers onto surfaces

Amelogenin is believed to be involved in controlling the formation of the highly anisotropic and ordered hydroxyapatite crystallites that form enamel. The adsorption behavior of amelogenin proteins onto substrates is very important because protein–surface interactions are critical to its function. We have previously used LRAP, a splice variant of amelogenin, as a model protein for the full-length amelogenin in solid-state NMR and neutron reflectivity studies at interfaces. In this work, we examined the adsorption behavior of LRAP in greater detail using model self-assembled monolayers containing COOH, CH₃, and NH₂ end groups as substrates. Dynamic light scattering (DLS) experiments indicated that LRAP in phosphate buffered saline and solutions containing low concentrations of calcium and phosphate consisted of aggregates of nanospheres. Null ellipsometry and atomic force microscopy (AFM) were used to study protein adsorption amounts and quaternary structures on the surfaces. Relatively high amounts of adsorption occurred onto the CH₃ and NH₂ surfaces from both buffer solutions. Adsorption was also promoted onto COOH surfaces only when calcium was present in the solutions suggesting an interaction that involves calcium bridging with the negatively charged C-terminus. The ellipsometry and AFM studies revealed that LRAP adsorbed onto the surfaces as small subnanosphere-sized structures such as monomers or dimers. We propose that the monomers/dimers were present in solution even though they were not detected by DLS or that they adsorbed onto the surfaces by disassembling or “shedding” from the nanospheres that are present in solution. This work reveals the importance of small subnanosphere-sized structures of LRAP at interfaces.     

Surface chemistry induces mitochondria-mediated apoptosis of breast cancer cells via PTEN/PI3K/AKT signaling pathway

Tumor cell can be significantly influenced by various chemical groups of the extracellular matrix proteins. However, the underlying molecular mechanisms involved in the interaction between cancer cells and functional groups in the extracellular matrix remain unknown. Using chemically modified surfaces with biological functional groups (CH₃, NH₂, OH), it was found that hydrophobic surfaces modified with CH₃ and NH₂ suppressed cell proliferation and induced the number of apoptotic cells. Mitochondrial dysfunction, cytochrome c release, Bax upregulation, cleaved caspase-3 and PARP, and Bcl-2 downregulation indicated that hydrophobic surfaces with CH₃ and NH₂ triggered the activation of intrinsic apoptotic signaling pathway. Cells on the CH₃- and NH₂-modified hydrophobic surfaces showed downregulated expression and activation of integrin β1, with a subsequent decrease of focal adhesion kinase (FAK) activity. The RhoA/ROCK/PTEN signaling was then activated to inhibit the phosphorylation of PI3K and AKT, which are essential for cell proliferation. However, pretreatment of MDA-MB-231 cells with SF1670, a PTEN inhibitor, abolished the hydrophobic surface-induced activation of the intrinsic pathway. Taken together, the present results indicate that CH₃- and NH₂-modified hydrophobic surfaces induce mitochondria-mediated apoptosis by suppressing the PTEN/PI3K/AKT pathway, but not OH surfaces. These findings are helpful to understand the interaction between extracellular matrix and cancer cells, which might provide new insights into the mechanism potential intervention strategies for tumor prognosis.     

Theoretical study on the functionalization of BC2N nanotube with amino groups

Using density functional theory calculations, we investigated properties of a functionalized BC₂N nanotube with NH₃ and five other NH₂-X molecules in which one of the hydrogen atoms of NH₃ is substituted by X = ?CH₃, ?CH₂CH₃, ?COOH, ?CH₂COOH and ?CH₂CN functional groups. It was found that NH₃ can be preferentially adsorbed on top of the boron atom, with adsorption energy of ?12.0 kcal mol^?1. The trend of adsorption-energy change can be correlated with the trend of relative electron-withdrawing or -donating capability of the functional groups. The adsorption energies are calculated to be in the range of ?1.8 to ?14.2 kcal mol^?1, and their relative magnitude order is found as follows: H₂N(CH₂CH₃) > H₂N(CH₃) > NH₃ > H₂N(CH₂COOH) > H₂N(CH₂CN) > H₂N(COOH). Overall, the functionalization of BC₂N nanotube with the amino groups results in little change in its electronic properties. The preservation of electronic properties of BC₂N coupled with the enhancement of solubility renders their chemical modification with either NH₃ or amino functional groups to be a way for the purification of BC₂N nanotubes.     

Insulin adsorption on functionalized silica surfaces: an accelerated molecular dynamics study

We study the influence of surface functionalization of a silica surface on insulin adsorption using accelerated molecular dynamics simulation. Three different functional groups are studied, CH₃, OH, and COOH. Due to the partial charges of these groups, the surface polarity of silica is strongly altered. We find that the adsorption energies of insulin change in agreement with the decreasing surface polarity. Conformational changes in the adsorbed protein and the magnitude of the molecular dipole moment in the adsorbed state are consistent with this result. We conclude that protein adsorption on functionalized polar surfaces is governed by the induced changes in surface polarity.     

The influence of surface wettability on the adhesion strength of settled spores of the green alga enteromorpha and the diatom amphora

In this paper we report on the effect of surface wettabilityon surface selection and adhesion properties of settled (adhered)spores of the biofouling marine alga Enteromorpha and cellsof the diatom Amphora, through the use of patterned self-assembledmonolayers (SAMs). The SAMs were formed from alkanethiols terminatedwith methyl (CH₃) or hydroxyl (OH) groups, or mixtures of thetwo, creating a discontinuous gradient of wettability as measuredby advancing water contact angle. In the case of Enteromorpha,primary adhesion, as measured by the transition from a motilespore to a settled, sessile organism, is strongly promoted bythe hydrophobic surfaces. On the other hand, adhesion strengthof the settled spores, as measured by resistance to detachmentin a turbulent flow cell, is greatest on a hydrophilic surface.In the case of Amphora, there is little influence of surfacewettability on the primary adhesion of this organism, but motilityis inhibited at contact angles