蓖麻蚕前胸腺细胞超微结构的变化与蜕皮激素分泌活动的关系

本研究叙述蓖麻蚕Philosamia cythia ricini四龄及五龄幼虫前胸腺蜕皮激素分泌活动各不同时期所显示的腺细胞超微结构变化。从幼虫蜕皮后至进入眠期之间的腺细胞结构可分为三个时期,(1)不活动期:细胞核呈圆形,核内密布染色质及核仁,细胞质内有结构完整的线粒体、粗面及滑面内质网、核糖体和高尔基氏体;细胞外围的细胞间区内有许多小囊泡及多泡囊。(2)活动期:细胞结构变化为细胞核膜出现内陷、外突,形成波浪形的核周膜;线粒体变形,出现内嵴稀疏的空心线粒体。(3)激素释放期:细胞核变形,形成若干长短不一向外伸出的指状突,有些伸达细胞边缘;其余细胞器退化,其后仅余残缺的高尔基氏体,稀疏的核糖体,线粒体的内崤逐渐消失,成为空腔扩大的及空腔内藏“膜轮”的线粒体,和一些溶解体及大形“膜轮”。     

蓖麻蚕前胸腺细胞超微结构的变化与蜕皮激素分泌活动的关系

本研究叙述蓖麻蚕Philosamia cythia ricini四龄及五龄幼虫前胸腺蜕皮激素分泌活动各不同时期所显示的腺细胞超微结构变化.从幼虫蜕皮后至进入眠期之间的腺细胞结构可分为三个时期,(1)不活动期:细胞核呈圆形,核内密布染色质及核仁,细胞质内有结构完整的线粒体、粗面及滑面内质网、核糖体和高尔基氏体;细胞外围的细胞间区内有许多小囊泡及多泡囊.(2)活动期:细胞结构变化为细胞核膜出现内陷、外突,形成波浪形的核周膜;线粒体变形,出现内嵴稀疏的空心线粒体.(3)激素释放期:细胞核变形,形成若干长短不一向外伸出的指状突,有些伸达细胞边缘;其余细胞器退化,其后仅余残缺的高尔基氏体,稀疏的核糖体,线粒体的内崤逐渐消失,成为空腔扩大的及空腔内藏“膜轮”的线粒体,和一些溶解体及大形“膜轮”.     

非洲狼尾草未受精无孢子生殖胚囊退化研究

为理解植物无孢子生殖胚囊未受精条件下的退化,对无孢子生殖植物非洲狼尾草未受精成熟胚囊中央细胞退化做了细胞形态学研究。没有受精的中央细胞退化时最显著的特点是细胞核产生核膜囊泡。核膜囊泡有两种类型:单层膜的囊泡和双层膜的囊泡,单层膜囊泡在细胞质中,双层膜囊泡在细胞核内。核膜囊泡有两种发生方式:1)核膜的外膜向细胞质一侧膨胀产生囊泡,囊泡进入细胞质;2)核膜向核内凹陷形成囊泡,囊泡进入细胞核。核膜囊泡类型与产生方式密切关联。核膜囊泡吞噬并消化包括线粒体在内的细胞质和核质。     

罗氏沼虾卵母细胞细胞器与卵黄发生的关系

作者研究了罗氏沼虾卵母细胞细胞器与卵黄发生的关系。细胞核物质通过核孔与细胞质进行物质交换,由核仁而来的核糖体前体物在细胞质中形成大量的核糖体。一部分核糖体附着在内质网囊泡的膜上,形成粗糙型内质网。粗糙型内质同囊泡具有合成和运输卵黄物质的功能。一部分核糖体是游离的,它们可在细胞质中合成致密蛋白质小颗粒,随后这些颗粒逐渐聚集融合成致密的卵黄粒。溶酶体可吞噬这些由游离核糖体形成的蛋白质颗粒团或其它膜状物,并将它们消化、融合,从而形成大的卵黄粒。部分线粒体参与了卵黄粒的合成并最终演变成卵黄体。微丝也参与了卵黄粒的形成。       

非洲狠尾草珠心细胞程序死亡过程的超微结构观察

用透射电子显微镜观察了非洲狼尾草心细胞衰亡过程,比较明显的结果是,染色质疑集,核周腔膨大呈袋状,内有包裹着核物质的内膜突起;有些内质网槽库膨大成囊泡,能吞噬细胞质;线粒体结构简化,内嵴消失。     

非洲狼尾草珠心细胞程序死亡过程的超微结构观察

用透射电子显微镜观察了非洲狼尾草珠心细胞衰亡过程,比较明显的结果是,染色质凝集,核周腔膨大呈袋状,内有包裹着核物质的内膜突起;有些内质网槽库膨大成囊泡,能吞噬细胞质;线粒体结构简化,内嵴消失.     

促红细胞生成素的分泌过程三维模式图

DNA经转录得到前体 m RNA,进一步剪切加工修饰得到成熟的 m RNA。核糖核蛋白体与 m RNA串连成多聚核糖核蛋白体 ,并通过信号识别颗粒及其受体结合于粗面内质网膜上 ,新合成的蛋白质进入内质网腔 ,经过加工修饰 ,以转运小泡的形式 ,运输到高尔基复合体。高尔基复合体由大囊泡、小囊泡和扁平囊组成 ,呈弯曲圆盘状。凸面称形成面或顺面 ,朝向胞核 ,凹面称分泌面或反面 ,朝向细胞表面 ,小囊泡多位于顺面 ,由粗面内质网出芽而来 ,运送新合成的蛋白质到扁平囊中 ,并不断补充扁平囊的膜结构。蛋白质在囊腔中经进一步加工修饰 ,由扁平囊两端和…     

荔枝雄花性别决定过程中细胞超微结构的变化

荔枝雄花雌蕊原基在大孢子母细胞减数分裂后开始衰退.内质网历经增生扩展,穿壁相连,同心缠绕,多条平行弯曲,不规则堆叠.内质网和高尔基体产生许多囊泡,囊泡在细胞内含物的降解和运输过程中起着重要的作用.线粒体在雌蕊原基细胞衰败的前、中期数量增加,后期分批降解.过氧化物酶体在雌蕊原基细胞衰败的中期紧挨核短暂出现.细胞核的染色质凝集断裂;核周腔扩大,形成胀泡;染色质趋边,外泄.细胞原生质表现出有序的、在膜包裹下的降解,首先是核糖体,而后依次是:过氧化物酶体、内质网、高尔基体、线粒体、核.雌蕊原基的衰败历程可能是一种程序性细胞死亡的过程.     

花生胚乳细胞化的超微结构观察

花生（ＡｒａｃｈｉｓｈｙｐｏｇｅａｅＬ．）心形胚期的胚乳游离核多瓣裂,或具长尾状结构。胚乳细胞质内有大量线粒体、质体、高尔基体、小泡及少量内质网。中央细胞壁有壁内突。球胚及心形胚期常见胚乳瘤。心形胚晚期,胚乳开始细胞化,胚乳细胞壁形成有３种方式,分别存在于不同的胚珠中：（１）从胚囊壁产生自由生长壁形成初始垂周壁,具有明显的电子密度深的中层,其生长主要靠末端的高尔基体小泡及内质网囊泡的融合。两相邻的自由生长壁末端或其分枝末端相连形成胚乳细胞。（２）核有丝分裂后产生细胞板,细胞板向外扩展并可分枝。间期的非姊妹核间也观察到形成了细胞板。小泡与微管参与细胞板的扩展,高尔基体和内质网是小泡的主要来源。细胞板的扩展末端相互连接,形成胚乳细胞的前身。小泡继续加入细胞板的组成,以后形成胚乳细胞壁。（３）胚乳细胞质中,出现一些比较大的不规则形的片段性泡状结构,它们可能来源于高尔基体小泡,这些片段性泡状结构随机相连形成细胞壁,未见微管参与。胚乳细胞外切向壁及经向壁上有壁内突。     

无蹼壁虎精子头部形成的研究

本文用透射电镜观察了无蹼壁虎精子头形成的过程。早期精细胞具有显著的高尔基复合体、线粒体集合及细胞质桥、接着高尔基体成熟面分泌出前顶体囊泡,并逐渐向核移动。以后精子形成可分四个时间：时间Ⅰ,当前顶体囊泡移至核膜时,核膜凹陷形成封闭的顶体囊泡,囊泡底部靠近核膜有一电子致密的顶体颗粒;时间Ⅱ,细胞核延长,顶体囊泡变扁平;时期Ⅲ,细胞核进一步延长,核内染色质纤维变粗并沿核纵轴方向排列有序;时间Ⅳ,精子发育     

Encystment ofBodo caudatus

Summary Before formation of the cyst wall, the food vacuoles are lost, the cell rounds up and the flagella lie close against the body in a flagellar groove. At this early stage, the contractile vacuole is very active, the Golgi apparatus is prominent and the basophilic cytoplasm is composed of closely packed ribosomes. As the cyst wall is secreted, layer by layer, the large Golgi apparatus is replaced by several smaller membrane stacks and mitochondrial changes occur involving local loss and modification of the cristae. Some parts of the mitochondrion undergo degenerative changes and may become surrounded by bacilliform bodies. These same bodies are also associated with small particles of sequestered cytoplasm which are present throughout the encystment process and are believed to be autophagic vacuoles. As the cyst wall thickens, cell shrinkage is manifest as a number of membrane invaginations. The final cyst wall is of uneven thickness and possesses a single operculum which is visible only by electron microscopy. Probable cyst wall precursor is found in small vesicles scattered throughout the cytoplasm.     

Ultrastructural study of encystation and excystation in Acanthamoeba castellanii

Encystation and excystation of Acanthamoeba castellanii were studied by transmission electron microscopy. The differentiation process was induced in asynchronous cultures grown axenically. Cytoplasmic vesicles containing a dense fibrous material very similar in appearance to the cyst wall were observed in trophozoites induced to encyst. When these trophozoites were incubated with calcofluor white m2r, fluorescence was observed in cytoplasmic vesicles, suggesting that the material contained in these vesicles corresponded to cyst wall precursors. Semithin cryosections of mature cysts with the same treatment showed fluorescence in the ectocyst and a less intense fluorescence in the endocyst, suggesting the presence of cellulose in both structures of the cyst wall. In mature cysts induced to excystation, small structures very similar to electron-dense granules (EDG) previously described in other amoebae were frequently observed. The EDGs were either sparsely distributed in the cytoplasm or associated with the cytoplasmic face of the plasma membrane. Many of them were located near the ostiole. In advanced phases of excystation, endocytic activity was suggested by the formation of endocytic structures and the presence of vacuoles with fibrous content similar to that of the cyst wall. Electron-dense granules in the process of dissolution were also observed in these vacuoles. Furthermore, the formation of a pseudopod suggests a displacement of the amoeba toward the ostiole.     

THE FINE STRUCTURE OF ACANTHAMOEBA CASTELLANII (NEFF STRAIN) : II. Encystment

Encysting cells of Acanthamoeba castellanii, Neff strain, have been examined with the electron microscope. The wall structure and cytoplasmic changes during encystment are described. The cyst wall is composed of two major layers: a laminar, fibrous exocyst with a variable amount of matrix material, and an endocyst of fine fibrils in a granular matrix. The two layers are normally separated by a space except where they form opercula in the center of ostioles (exits for excysting amebae). An additional amorphous layer is probably present between the wall and the protoplast in the mature cyst. Early in encystment the Golgi complex is enlarged and contains a densely staining material that appears to contribute to wall formation. Vacuoles containing cytoplasmic debris (autolysosomes) are present in encysting cells and the contents of some of the vacuoles are deposited in the developing cyst wall. Lamellate bodies develop in the mitochondria and appear in the cytoplasm. Several changes are associated with the mitochondrial intracristate granule. The nucleus releases small buds into the cytoplasm, and the nucleolus decreases to less than half its original volume. The cytoplasm increases in electron density and its volume is reduced by about 80%. The water expulsion vesicle is the only cellular compartment without dense content in the mature cyst. The volume fractions of lipid droplets, Golgi complex, mitochondria, digestive vacuoles, and autolysosomes have been determined at different stages of encystment by stereological analysis of electron micrographs. By chemical analyses, dry weight, protein, phospholipid, and glycogen are lower and neutral lipid is higher in the mature cyst than in the trophozoite.     

Wall formation in the saprolegniales

Summary The primary and secondary cysts of Saprolegnia ferax and the secondary cysts of Dictyuchus sterile have a two layered wall structure, the outer layer of which bears various types of spines. These spines, and the outer wall layer are derived from preformed structures (bars) found in the cytoplasm prior to encystment. Golgi derived vesicles appear to contribute to the inner layer of the primary cyst wall of S. ferax. The outer surface of the secondary cyst walls of this species has fibrils which are not embedded in matrix material.     

Ribonucleoprotein-Containing Vesicles in Cysts of Naegleria gruberi*

SYNOPSIS. Ultraviolet microscopy and electron microscope autoradiography were used to study ribonucleoprotein in cysts of Naegleria gruberi. The absorption maximum for cysts is at 265 nm with little detectable absorption occurring at 295 nm. Pre-cystic trophozoites absorb less strongly than the cysts at 265 mm. Acridine orange staining indicated concentrations of ribose nucleic acid or ribonucleoprotein in the cytoplasm of young cysts. The dye stained discrete vesicles in the cytoplasm. Tritiated uridine and tritiated proline were used to follow changes in RN-protein at encystment. Label was incorporated into vesicles filled with ribosome-like particles. These are presumably the sites of acridine orange staining. Relatively little label was associated with the cyst cytoplasmic matrix; most of the silver grains lay over the nucleus and cytoplasmic organelles. The vesicles are believed to represent autophagosomal-type vacuoles with the contents derived from breakdown of organelles such as mitochondria. The path of label into the vesicles is via lysis of labeled cytoplasmic organelles. The RN-protein vesicles of Naegleria gruberi cysts are compared to the chromatoid bodies of Entamoeba invadens. It is concluded that, tho differences in detail are present, the role of the structures in the cysts is probably the same. They are a ready source of amino acids and ribosomes in a dedifferentiated or pool state to be used for synthetic reactions that accompany resumption of trophic existence.     

The differentiation of cellular structure during encystment in the soil hypotrichous ciliate Australocirrus cf. australis (Protista,Ciliophora)

Ciliates are able to form resting cysts as a survival strategy in response to stressful environmental factors. Studies on the characteristics of cellular structure during encystment may provide useful information for further understanding of the regulatory mechanism of cellular patterns and supply new clues regarding the phylogeny of ciliates. Scanning and transmission electron microscopies were used to observe the ultrastructure of cells during encystment of the soil ciliate Australocirrus cf. australis. The dedifferentiation of ciliature was revealed for the first time. Ciliary shafts first shortened, and the remaining ciliature, including basal bodies and the fibrillar cirral basket, retracted into the cytoplasm and was surrounded by the autophagic vacuoles and then gradually digested. A large number of autophagic vacuoles were observed in mature resting cysts. Autophagy might not only be necessary for the differentiation of cellular structures during encystment but might also be important to sustain the basic life activities in the resting stage. Australocirrus cf. australis formed a kinetosome-resorbing cyst and contained four layers in the cyst wall: the ectocyst, mesocyst, endocyst and granular layer. The ciliature resorbing state and the number of layers in the cyst wall were consistent with those found in other oxytrichous ciliates. However, the phenomenon wherein the two macronuclear nodules are not fused during encystment is not commonly observed among oxytrichids. Additionally, the octahedral granules in the mesocyst of this species exhibit different morphology from the congeners.     

Differentiation During Encystment and Excystment in Oxytricha fallax*

During encystment of Oxytricha fallax, a wall composed of 4 distinct layers, each derived from a different kind of endoplasmic vesicle, is formed between the 2 unit membranes that cover the vegetative cell. Numerous autophagic vacuoles arise in the endoplasm and later (during excystment undergo internal changes comparable to those characteristic of food vacuoles. Mitochondria aggregate into a band. The 2 macronuclei fuse and their nucleoli become homogeneous. Except for the 2 cell membranes, all visible cortical structures, including cilia, kinetosomes, and microtubules, disappear. Despite the absence of visible ciliature in the mature cyst, the various primordia of the normal vegetative ciliature arise during excystment in the same positional relations to one another as is characteristic of developments during cell division.     

冠突伪尾柱虫营养期和形成包囊期间细胞的超微结构

冠突伪尾柱虫营养细胞中含有轴杆样结构。细胞形成包囊期间,胞质内发生自噬作用,并产生由这聚集在一起组成的高尔基体,在高尔基体内其分泌物质聚集成高电子密度的嗜锇晶体。细胞分化的结果形成含膜粒层,内层壁和外层壁的“尾柱虫类包囊”。     

Giardia muris: ultrastructural analysis of in vitro excystation

Giardia muris cysts were examined by transmission electron microscopy before treatment, after induction, and at timed intervals during the incubation phase of in vitro excystation. Untreated G. muris cysts had a thick cyst wall composed of a fibrous outer wall and a thin, electron-dense inner membrane which extended from the trophozoite plasma membrane. The cytoplasm was devoid of endoplasmic reticulum, Golgi bodies,and mitochondria. Numerous large vacuoles were present within the ectoplasm just beneath the plasma membrane in untreated cysts. Following induction these cysts lacked ectoplasmic vacuoles. Concurrently, numerous membrane bound vesicles were seen in the peritrophic space closely adhering to the surface of the trophozoite. These vesicles appear to be of cytoplasmic origin. The cytoplasm of fully excysted trophozoites lacked ectoplasmic vacuoles but displayed well-developed ribbons of microtubular bodies, probably precursors of ventral disk, lateral flange, and median bodies and also contained extensive granular endoplasmic reticulum. No more than two nuclei were observed within each organism. The earliest excysted organisms were observed 0-5 min after incubation had begun and most organisms had excysted within 10 min. Cytokinesis occurred only after excystation was complete.     

EXOCYTOSIS OF LATEX BEADS DURING THE ENCYSTMENT OF ACANTHAMOEBA

Cells of Acanthamoeba castellanii (Neff) are known to form mature cysts characterized by a cellulose-containing cell wall when transferred to a nonnutrient medium. Amebas which engulfed latex beads before encystment formed mature cysts essentially devoid of bead material. The encystment of bead-containing cells appeared to be similar to that of control cells since no important differences between the two were observed with respect to cellular levels of glycogen or protein, cellulose synthetase activity, the amount of cyst wall polysaccharide formed, or the percentage of cysts formed. Actinomycin D and cycloheximide inhibited encystment as well as bead expulsion. Ultrastructural analysis revealed that the beads, which initially were contained in phagocytic vesicles, were released from the cell by fusion of vesicular membranes with the plasma membrane. Exocytosis was observed in cells after 3 hr of encystment, with most of the beads being lost before cyst wall formation. Each bead-containing vesicle involved in expulsion was conspicuously demarcated by an area of concentrated cytoplasm, which was more homogeneously granular than the surrounding cytoplasm. Beads were not observed in the cytoplasm of mature cysts but were occasionally found in the cyst wall.