微丝

生命在于运动,各类生物有机体都在进行运动。动物和人有肌肉,肌肉收缩引起运动。构成肌肉的是肌纤维,肌纤维内有肌原纤维,肌原纤维内有粗细两种纤维,粗纤维含有肌球蛋白,细纤维含有肌动蛋白,两种蛋白相互滑动,使肌肉进行收缩运动。肌球蛋白和肌动蛋白不但分布在肌肉细胞里,还广泛地分布在非肌肉细胞里。在非肌肉细胞里它们以微丝的形式存在。肌动蛋白在2M Mg~(++)或0.1M K~+存在下,在体布能形成微丝,或者以未聚合的肌动蛋白单体的形式存在。各类真核细胞都发现有微丝,动植物细胞的生长和细胞的有丝分裂,细胞质的流动,以及变形虫和粘菌的变形运动,这些都有微丝的功能。     

高等植物体内的肌动蛋白

植物肌动蛋白是植物细胞生物学领域发展起来的热点,它涉及植物细胞的分裂机制。细胞运动,细胞器运动,细胞的极性,细胞空间形状的维持,物质运输等,对高等植物肌动蛋白的性质,功能,研究方法及分子生物学领域的研究作了综述。并对该领域存在的问题及应用前景作了展望。     

肌动蛋白和肌动蛋白基因的研究进展

细胞质来源肌动蛋白,构成细胞微丝,肌肉中的肌动蛋白主要是纤维形式即F－肌动蛋白。肌动蛋白基因编码序列是高度保守的,而非编码序列有较大的差异,反映其进化上的时间进程。对该基因的研究越来越受到重视,尤其在分子生物学中,常把它当作基因表达研究的参考标准。     

洋葱鳞茎中肌球蛋白和肌动蛋白的免疫化学鉴定

制备了粘菌肌动蛋白抗血清和鸡骨骼肌肌球蛋白抗血清。用这两种抗血清,经对流免疫电泳,火箭电泳及酶联免疫吸附分析,证明了高等植物洋葱鳞茎中肌球蛋白和肌动蛋白的存在。     

高等植物自交不亲和反应中花粉管信号传导研究进展(综述)

高等植物自交不亲和反应是由基因控制、避免发生自花授粉的一种机制。本文介绍以虞美人为主的高等植物在自交不亲和反应中肌动蛋白骨架的动态变化及Ca2 的时空变化,着重阐述花粉管生长被抑制的最初信号传导。     

谷子肌动蛋白基因的克隆及序列分析

以谷子 (Setariaitalica)为材料 ,提取总RNA。根据植物肌动蛋白基因编码区的两端的保守序列设计了简并引物 ,用 5’RACE方法扩增出了谷子肌动蛋白基因编码区序列。以豌豆肌动蛋白cDNA作探针进行的Southern杂交分析表明扩增出了目的基因。将所获得的片段克隆到T载体后进行测序 ,序列分析结果表明 :谷子肌动蛋白基因的编码区长 1 1 3 1个核苷酸 ,编码了 3 77个氨基酸 ;所得序列 (命名为MIAc)与GenBank中注册的肌动蛋白基因序列的相似性均在 6 0 %以上 ,与其它肌动蛋白氨基酸序列的相似性达 89%以上。根据高等植物肌动蛋白序列相似性重建了进化树 ,表明谷子肌动蛋白与水稻肌动蛋白异型体RAc2和RAc3之间的亲缘关系最为密切 ,在进化过程中分化时间最为接近     

谷子肌动蛋白基因的克隆及序列分析

以谷子（Setaria italica）为材料,提取总RNA。根据植物肌动蛋白基因编码区的两端的保守序列设计了简并引物,用5'RACE方法扩增出了谷子肌动蛋白基因编码区序列。以豌豆肌动蛋白cDNA作探针进行的Southern杂交分析表明扩增出了目的基因。将所获得的片段克隆到T载体后进行测序,序列分析结果表明：谷子肌动蛋白基因的编码区长1131个核苷酸,编码了377个氨基酸;所得序列(命名为MIAc)与GenBank中注册的肌动蛋白基因序列的相似性均在60%以上,与其它肌动蛋白氨基酸序列的相似性达89%以上。根据高等植物肌动蛋白序列相似性重建了进化树,表明谷子肌动蛋白与水稻肌动蛋白异型体RAc2和RAc3之间的亲缘关系 最为密切,在进化过程中分化时间最为接近。     

细胞骨架(续)

(四)微丝和微管的功能微丝和微管的功能就三个问题来谈:细胞形状的维持、与非肌肉细胞运动的关系和与细胞分裂的关系。这里要谈到两个运动系统即肌动蛋白—肌球蛋白系统和微管—二联臂(dynein)系统。非肌肉细胞的运动机制,目前多从肌原纤维的收缩蛋白在非肌肉细胞中的分布等方面进行探讨。一旦肌节的单一蛋白鉴定和纯化,就可在非肌肉细胞中寻找是否有相同或近     

决定细胞形状和运动性的蛋白质 palladin

Palladin 是肌动蛋白结合蛋白家族的新成员,广泛分布于平滑肌、中枢神经系统和胚胎的各种组织中,其主要的生物功能是参与构建肌动蛋白骨架系统,并在细胞骨架的动态变化中起作用 . 在肌动蛋白细胞骨架中 palladin 与 alpha- 辅肌动蛋白共存在 . 目前发现, palladin 在决定细胞的形态和迁移或运动等过程中起关键的作用 . 在转移性癌细胞和中枢神经受损伤后的星形胶质细胞中,都有 palladin 的特殊表达 . Palladin 的表达使星形胶质细胞形成了神经胶质疤痕 .     

肌切蛋白的结构与功能多样性

肌切蛋白（scinderin）是一种重要的肌动蛋白结合蛋白,在哺乳动物和脊椎动物中广泛表达.肌切蛋白作为凝溶胶蛋白超家族的成员之一,通过肌动蛋白丝切割、肌动蛋白聚集等方式来控制肌动蛋白的结构.肌切蛋白生物活性具有多样性,除影响肌动蛋白丝重组外,肌切蛋白还参与细胞胞吐作用、调节细胞运动、细胞分化等细胞活动.此外,肌切蛋白在慢性炎症、凝血过程、免疫性疾病和肿瘤发生发展中也发挥了重要作用.本文对肌切蛋白的结构特点、参与调节细胞的功能和机制进行概述.     

烟草花粉母细胞减数分裂前期I肌动蛋白的免疫细胞化学定位

The Pollen Mother Cells of Nicotiana Rustica L. were studied using the techniques of immunofluorescence microscopy and protein A-colloidal gold IEM. Immunofluorescence microscopy indicates the presence of actin in both nuclei and cytoplasm. IEM observation shows that gold particles are present in cytoplasm, chromatin and cytomictic channels. These results indicate that actin has some relation with chromatin condensing at synizesis. Moreover, actin may also play an important role in cytomixis.     

Ultrastructural immunolocalization of actin in a fungus

Summary We have successfully localized fungal actin for the first time using immuno-electron microscopy and hyphal tips of the rice blast pathogenMagnaporthe grisea. Following ultrarapid freezing, samples were processed in a novel substitution fluid of 10% acrolein in anhydrous ethanol and embedded in LR White resin. A monoclonal anti-actin antibody, previously shown to recognizeM. grisea actin, bound specifically to filasomes concentrated in the peripheral cytoplasm of subapical regions, and to the core-region of the Spitzenkörper.Abbreviations IEM immuno-electron microscopy - TEM transmission electron microscopy     

嫁接早期IAA在西葫芦/南瓜嫁接面处薄壁细胞和维管分子中的免疫细胞学定位

采用免疫胶体金法对IAA在西葫芦／南瓜离体茎段嫁接早期发育时期在嫁接面处的分布进行了超微结构水平的定位。电镜观察表明在嫁接面处的薄壁细胞中IAA主要定位于细胞核、质体、内质网等细胞器上。在高尔基体、线粒体、细胞壁和液泡中,未发现胶体金颗粒的标记。在分化中的管状分子中,胶体金颗粒位于次生壁上和细胞质中。在筛分子分化过程中,IAA主要定位于筛板、筛孔和细胞质中。在伴胞中有较高的金颗粒密度。对于IAA在嫁接体维管分子分化过程中的作用进行了讨论。     

肌动蛋白存在于蚕豆细胞核和染色体中

以兔抗肌动蛋白抗体为一抗,FTTC偶联的羊抗兔IgG抗体为二抗进行间接免疫荧光实验,观察到蚕豆(Vicia faba L.)根端分生组织中完整的细胞核和染色体均有明亮荧光。用抗肌动蛋白抗体和蛋白A-胶体金进行标记的免疫电镜实验结果表明,金颗粒分布在蚕豆细胞核中,集缩染色质和核仁中金颗粒较多。经DNaseI消化和2 mol/L NaCl处理得到去除DNA和组蛋白的细胞核和染色体。免疫荧光实验结果指出,去除DNA和组蛋白的细胞核和染色体与抗肌动蛋白抗体呈阳性反应。上述结果说明,肌动蛋白不仅存在于完整的蚕豆细胞核和染色体中,而且存在于去除DNA和组蛋白的蚕豆细胞核和染色体中。另外,用抗原肌球蛋白抗体所做的免疫荧光标记结果表明,原肌球蛋白也存在于蚕豆细胞核和染色体中。对高等植物细胞核和染色体以及核骨架和染色体骨架是否含有肌动蛋白等问题进行了讨论。     

Immunocytochemical localization of actin in the nucleolus of rat oocytes

Summary— In order to determine the localization of actin, growing and fully grown rat oocytes were immunocytochemically examined using a post-embedding ultrastructural protein-A gold technique. In quiescent oocytes, the nucleoplasm showed slightly lower levels of actin signal when compared to the surrounding cytoplasm. The highest levels of labeling were found on nucleoli showing a reticular type morphology. In oocytes at the diakinesis stage in which nucleolar compaction had occurred, the levels of labeling increased by 5–6 times those found in quiescent oocytes. Except for conspicuous accumulation of actin under the plasma membrane, compact nucleoli had significantly higher levels of labeling when compared with those found on the general cytoplasm, while the nucleoplasm with homogeneously dispersed chromatin showed significantly lower levels of associated actin signal than the general cytoplasm. In oocytes at metaphase I, the cytoplasmic region had comparable or lower levels of labeling than the cytoplasm of oocytes at diakinesis. The meiotic spindle embedded in material with medium electron density showed a similar level of labeling as the surrounding cytoplasm. On the other hand, significantly higher levels of associated actin were observed on the chromosomes of metaphase I. The actin signals were dispersed over the chromosomes and not concentrated on a specific region. These results suggest that nuclear actin may be involved in the process of chromosome construction and also the formation of the compacted structure of the nucleolus.     

Evaluation of immunoelectron microscopic techniques in the study of basement membrane antigens

 Recent technical advances in immunoelectron microscopy (IEM), including methods of pre- and postembedding IEM and cryoultramicrotomy, have helped to elucidate the precise ultrastructural localization of various basement membrane-related molecules. Our objective was to evaluate the advantages and disadvantages of several different techniques for studying the ultrastructural organization of basement membrane components. We found that, while ”on-surface” immunolabeling of postembedding IEM and cryoultramicrotomy with anti-type IV collagen or anti-laminin-5 antibody clearly demonstrated dense labeling on the lamina densa, preembedding IEM with a 1-nm ultra-small gold probe showed labeling only on the epidermal and/or dermal surfaces of the lamina densa, with no specific gold particles being seen within the lamina densa itself. These results indicate that even ultra-small colloidal gold-labeled antibody fails to penetrate the lamina densa in preembedding IEM. However, labeling with a GB3 monoclonal antibody against laminin-5 was demonstrable with preembedding IEM and cryoultramicrotomy, but not with post-embedding IEM, probably due to a loss of antigenicity. These results confirm the advantages and limitations of these techniques of IEM and emphasize the importance of using different techniques of IEM in determining the precise ultrastructural distribution of basement membrane antigens. Accepted: 30 January 1998     

Ultrastructural evidences of HCV infection in hepatocytes of chronically HCV-infected patients

In this study, 13 samples of liver biopsies from patients with chronic hepatitis C were studied by transmission electron microscopy (EM) and immunoelectron microscopy (IEM). The 13 biopsies showed ultrastructural cell damage typical of acute viral hepatitis. In four of the 13 liver biopsies enveloped virus-like particles (VLPs) inside cytoplasmic vesicles and in the cytoplasm of hepatocytes were observed. We also detected the presence of unenveloped VLPs mainly in the cytoplasm and in the endoplasmic reticulum. IEM using anti-core, E1 and E2 monoclonal antibodies (mAbs) confirmed the specific localization of these proteins, in vivo, inside cytoplasm and endoplasmic reticulum. Thus, this work provided evidence for hepatocellular injury related to HCV infection. It also suggested the presence of HCV-related replicating structures in the cytoplasm of hepatocytes and raised the possibility of hepatitis C virion morphogenesis in intracellular vesicles.     

Localization of cytoskeletal proteins in Pneumocystis carinii by immuno-electron microscopy

Pneumocystis carinii causes serious pulmonary infection in immunosuppressed patients. This study was undertaken to observe the cytoskeletal proteins of P. carinii by immuno-electron microscopy. P. carinii infection was experimentally induced by immunosuppression of Sprague-Dawley rats for seven weeks, and their lungs were used for the observations of this study. The gold particles localized actin, tropomyosin, and tubulin. The actin was irregularly scattered in the cytoplasm of the trophic forms but was much more concentrated in the inner space of the cell wall of the cystic forms called the inner electron-lucent layer. No significant amount of tropomyosin was observed in either trophic forms or cystic forms. The tubulin was distributed along the peripheral cytoplasm and filopodia of both the trophic and cystic forms rather than in the inner side of the cytoplasm. Particularly, in the cystic forms, the amount of tubulin was increased and located mainly in the inner electron-lucent layer of the cell wall where the actin was concentrated as well. The results of this study showed that the cell wall of P. carinii cystic forms is a structure whose inner side is rich in actin and tubulin. The location of the actin and tubulin in P. carinii suggests that the main role of these proteins is an involvement in the protection of cystic forms from the outside environment by maintaining rigidity of the cystic forms.     

DDX6 localizes to nuage structures and the annulus of mammalian spermatogenic cells

The localization of DEAD (Asp-Glu-Ala-Asp) box helicase 6 (DDX6) in spermatogenic cells from the mouse, rat, and guinea pig was studied by immunofluorescence (IF) and immunoelectron microscopy (IEM). Spermatogenic cells from these species yielded similar DDX6 localization pattern. IF microscopy results showed that DDX6 localizes to both the nucleus and cytoplasm. In the cytoplasm of spermatogenic cells, diffuse cytosolic and discrete granular staining was observed, with the staining pattern changing during cell differentiation. IEM revealed that DDX6 localized to the five different types of nuage structures and non-nuage structures, including small granule aggregate and late spermatid annuli. Nuclear labeling was strongest in leptotene and zygotene spermatocytes and moderately strong in the nuclear pocket of late spermatids. DDX6 also localized to the surface of outer dense fibers, which comprise of flagella. The results show that DDX6 is present in nuage and non-nuage structures as well as nuclei, suggesting that DDX6 has diverse functions in spermatogenic cells.     

Actin is Immunolocalized in the Nuclei and Chromosomes of Vicia faba

Meristematic cells of Vicia faba L. were labeled with rabbit anti-actin antibody and FITC-conjugated goat anti-rabbit lgG antibody and observed with fluorescence microscopy. Both the nuclei and chromosomes sent forth distinctive fluorescence, indicating that actin is present in the nuclei and chromosomes. Sections were reacted with the anti-actin antibody and protein A-colloidal gold and observed with transmission electron microscopy. Gold particles were found over the whole nuclei, and a lot of particles were concentrated in condensed chromatin areas and nucleoli, confirming the observations with the fluorescence microscopy. V. faba nuclei and chromosomes were treated with DNase Ⅰ and 2 mol/L NaC1, and DNA and histone-depleted nuclei and chromosomes were obtained. Indirect immunofluorescence tests showed that the DNA and histone-depleted nuclei and chromosomes reacted positively with the anti-actin antibody. These results demonstrated that actin exists not only in intact nuclei and chromosomes but also in DNA and histone-depleted nuclei and chromosomes of V. faba. In addition, the authors' results indicate that tropomyosin is present in the nuclei and chromosomes of V. faba. Presence of actin in nuclei and chromosomes as well as in DNA and histone-depleted nuclei and chromosomes of higher plants is discussed.