【作者】 李其利；

【导师】 顾福康；

【作者基本信息】 华东师范大学 ， 动物学， 2012， 硕士

【摘要】 原生动物纤毛虫在环境条件突然变化时,经常会发生形成包囊(encystment)的过程。期间,纤毛虫细胞结构发生显著的脱分化,细胞从伸展运动状态变为充分收缩的圆球样非运动状态,细胞质胞器及核器的形态和功能也伴随着产生激烈的变化。关于纤毛虫形成包囊过程中细胞形态结构与功能的变化,已经受到生物学不同领域研究者的关注。腹毛类纤毛虫是纤毛虫中一类细胞结构高度进化的类群,特别是其细胞内含有发达的微管类细胞骨架,对细胞运动、细胞形态的维持和细胞各种功能的发挥等起着至关重要的作用,研究微管类细胞骨架在纤毛虫包囊形成过程中的分化特征,已经成为探索真核细胞的结构与功能及其细胞调控的一个重要方面。本文以腹毛目纤毛虫异毛虫(Allotrichacurdsi)为材料,应用扫描电镜术和透射电镜术,在显示营养期纤毛虫细胞结构的基础上,对其包囊形成过程中细胞皮层及皮层纤毛器的分化进行了较细致的比较观察,获得了该纤毛虫包囊形成过程中细胞皮层纤毛器及胞质细胞器分化的超微结构特征,为深入阐明细胞形成包囊的形态学及细胞结构分化与调控等提供了新的资料。1.营养细胞超微结构观察应用扫描电镜术显示,凯氏异毛虫营养细胞呈长椭圆形,背腹扁平且背部微隆,尾部削尖并向左上方微翘。营养细胞纤毛器发达,腹面纤毛器中,口纤毛器由口围带和波动膜组成；额腹横棘毛分化明显；左缘棘毛恒为1列,右缘棘毛多列；背面纤毛器中,背触毛6列,每个背触毛单元由未长出纤毛的裸毛基体和长出纤毛的毛基体组成；尾棘毛3根。纯系细胞培养中偶见异常超大个体,一般其体积是正常胞体的2-3倍。应用透射电镜术显示,凯氏异毛虫营养细胞中,除纤毛器结构外,异毛虫表膜下表质层中有微管对其加固；细胞内多空白区域,基质区内含有丰富的线粒体、食物泡、内质网等胞器；大核中核仁和染色质分散分布其中。凯氏异毛虫营养期细胞近口端背皮层表膜下排列许多呈不规则球形、外围一层波浪状的质膜、内含致密的晶状物质的胞器,其形态结构特征与大尾柱虫和双轴虫的粘液泡相近,推测其为粘液泡射出胞器。本文所得结果不仅为深入认识凯氏异毛虫细胞结构特征及其分类地位提供详细资料,也为研究在特殊生理条件下凯氏异毛虫形成包囊过程中细胞结构分化及其细胞质衍生物形成特征提供基础资料。2.包囊形成过程中皮层纤毛器和胞器变化应用扫描电镜术显示,凯氏异毛虫形成包囊的过程中细胞形态发生显著变化,细胞由长扁平形团缩为橄榄球形,继续脱水变圆呈球形；细胞皮层纤毛亦发生明显变化,背触毛单元中未长出纤毛的裸毛基体再分化出纤毛,形成具有2根纤毛的背触毛单元,背、腹面纤毛随细胞团缩而螺旋排列在细胞表面,高度分化的纤毛簇随细胞包囊逐步形成而分散瓦解,纤毛基部连同细胞皮层形成按一定间隔成规则排布的突起,包囊形成。休眠包囊形似松球,其表面布满规则排布的扁平菱形突起,包囊底部凹陷起附着作用。当环境未能达到脱包囊的要求时,包囊发生瓦解。应用透射电镜术显示,形成包囊后的纤毛虫,其细胞皮层纤毛器及与其相联系的微管类骨架消失,形成“毛基体吸收型包囊”。包囊壁可分为四层,其中外层壁的表面有纤维物质,纤维结构在包囊形成的后期逐渐延展成突起,在休眠包囊表面均匀排布,其形态与扫描电镜下观察到的包囊表面的突起相吻合；休眠细胞内线粒体的管状嵴结构模糊,其他细胞器数目锐减；大、小核的染色质浓聚,呈高电子密度状态。同时,在休眠细胞内可见自噬泡类细胞器,说明存在于包囊时期的自噬泡结构可能是食物泡的另一种特殊的结构状态,它的作用可能为休眠细胞提供基本的能量和营养来源。研究异毛虫包囊形成过程中皮层及皮层纤毛器的分化,所得结果为深入了解特殊生理条件下纤毛虫细胞结构的分化特征及分化过程中形成特殊的细胞质衍生物特征提供了较详细的资料。更多还原

【Abstract】 When the environment sudden changes and has bad impact on the life activities of hypotrich ciliates, the process of encystment is common, which takes an important effect on its survival. During the process, the cell structure of hypotrich ciliates happen to significant differentiation, the cells gradually stop the movement and feeding, and then shrink of cells, the cytoplasm organelles and nuclears are also associated with drastic changes. Study on the differentiation of microtubular cytoskeletons has been concerned by biology researchers in different fields. Ciliates are the most advanced heterotrophic protist, especially it has the complicated microtubular cytoskeleton, which plays important role on keeping the cell morphology, the movement and all kinds of functions. Study of the characteristics of microtubules cytoskeleton differentiation in the process of encystment, has become an important aspect to explore the structure and function of eukaryotic cells and regulation of cell. In this study, we used Allotricha curdsi as the experimental material, applying scanning electron microscopy(SEM) and transmission electron microscopy(TEM), to observe the normal cell structure and the formation of encystment and compare the differerntiation of cortex structure and cytoplasm organelles between normal cell and resting cell of Allotricha curdsi, Results are as follows:1. The ultrastructure of normal cell of Allotricha curdsiThe details of the morphology and morphogenesis of the hypotrichous ciliate Allotricha curdsi were observed with SEM in this study:The normal cell has long oval shape, the ventral side is flat and its dorsal side is distinctly vaulted. The tail sharpening and the left upper part micro become warped. The cortex ciliature of the Allotricha curdsi is developed and consists of adoral zone of membranelles(AZM), undulating membranes(UM), front-ventral-transverse cirri(FVTC), left and right marginal cirri(L-and-RMC), caudal cirri(CC) and dorsal kineties(DK). The UM comprises a endoral membrane (EM) and a paroral membrane(PM), which both start at the base of the AZM. A LMC and three RMC are located in the ventral side of the ciliate. The CC consists of three cirris were recognizable and distinct from marginal cirri. Six rows of DK locate in the dorsal side of the ciliate, each unit of DK has a cilia kinetosome and a barren kinetosome. there are exception large individuals occasionally in pure department cell culture, general the volume is the normal2-3times.The internal ultrastructure of Allotricha curdsi was observed by using TEM. We found that the surface membrane was composed of the plasma membrane and the cell membrane. There was dense fiber bundles close to ventral surface membrane to reinforce the structure. We also observed that the cytoplasm is full of the cortical pellicle, cytoplasm beneath pellicle, cortical microtubular organelles and other organelles. The cortical organelles in ciliates have some differentiation and specialization. Extrusomes play an important role in the life activities of ciliates. The study on morphological characteristics, morphogenesis, and the location of extrusomes in hypotrich ciliates can supply the new data for further elucidation of the relationship between function of organelles and cellular activity.2. The differentiation of cilia and cytoplasm during encystment of Allotricha curdsiThe details of the differentiation of cortex and cilia during the encystment of the hypotrichous ciliate Allotricha curdsi was observed with SEM. The result showed that: During the cells transforming from the long oval shape into soccer form, the dedifferentiation of microtubular organelles on ventral side happened, meanwhile, the unit of dorsal bristle started to redifferentiation with a new cilia growing from the previously barren kinetosome. As cells contracted further, the cyst wall began to emerge and the protrusions arranged regularly on the cyst surface simultaneously. After the cyst changing from cactus-like shape to spiral-like shape, the resting cyst formed. Without improving the culturing environment, the resting cysts finally disintegrated and disappeared. The results present in this paper provided new information for better understanding the differentiation of the cilia structure and the formation of the cytoplasm derivatives in special physiological conditions.The details of the differentiation of organelles and nuclear ultrastructure during encystment of hypotrichous ciliate Allotricha curdsi was observed with TEM. During encystment, most of the cortex microtubular is disappeared. The cyst of Allotricha curdsi contains large amounts of mitochondria cyst caterpillars and autophagic vacuoles, which might be related to food digestion and energy storage. Largest nuclear elongated cylindrical, showing wavy. some family reunion into a high electron density of the sizes of the clumps, nucleolus high number of scattered large nucleus; The nuclear pore-like structure made the nuclear membrane into the dotted line. After the formation of cysts, cyst wall became four layers. Cysts have two autophagic vacuoles:organelle autophagic vacuoles, and cytoplasmic autophagic vacuoles. To sum up, the findings in this research are of significantly scientific importance for the further elucidation of the specificity of cytoarchitectures and the relationship between the cytoarchitectures and their functions, the deep of the knowledge about the occurrence of encystment, the changes of cortical structure and the mechanisms of cell regulation in cellular activity of ciliates.更多还原