西瓜不同发育时期的助细胞超微结构的变化

被子植物胚囊的“雌性生殖单位”,已在多种植物上进行了超微结构的观察,但大多都以卵细胞受精前后的结构变化为主要研究内容。对于“雌性生殖单位”中的另一重要成员——助细胞,在不同发育状态下其结构变化的详细资料不多,尤其是助细胞退化后的物质去向,少见报道。本研究主要观察了西瓜不同发育时期(受精前后)、不同发育状态(柱头授粉和未授粉)的助细胞超微结构,以期为研究助细胞在双受精中所起作用提供新的资     

山溪鲵卵黄发生的显微与超微结构

用光镜和透射电镜观察了山溪鲵（Batrachuperus pinchonii)不同发育时期卵母细胞的显微与超微结构,特别注意了与卵黄发生相关的细胞器变化。结果表明,类核周体为线粒体、高尔基体、内质网等膜性细胞器聚集的场所;线粒体自身也可演变成卵黄前颗粒,参与构成卵黄小板的成分;吞饮泡和髓样小体是卵母细胞利用外源卵黄物质的中间媒介。经过与其他动物卵黄发生过程相比较,认为非哺乳脊椎动物卵黄发生是卵母细胞在多种细胞器参与下整体活动的结果,不是经由单一的模式或途径形成,因此呈现发生上的多元化;不同物种在卵黄发生中分别采取与各自相适应的模式或途径。     

东方扁虾卵子发生的超微结构

根据卵细胞的形态、内部结构特征及卵母细胞与滤泡细胞之间的关系,东方扁虾的卵子发生可划分为卵原细胞、卵黄发生前卵母细胞、卵黄发生卵母细胞和成熟卵母细胞等四个时期。卵原细胞胞质稀少,胞器以滑面内质网为主。卵黄发生前卵母细胞核明显膨大,特称为生发泡;在靠近核外膜的胞质中可观察到核仁外排物。卵黄发生卵母细胞逐渐为滤泡细胞所包围;卵黄合成旺盛,胞质中因而形成并积累了越来越多的卵黄粒。东方扁虾卵母细胞的卵黄发生是二源的。游离型核糖体率先参与内源性卵黄合成形成无膜卵黄粒。粗面内质网是内源性卵黄形成的主要胞器。滑面内质网、线粒体和溶酶体以多种方式活跃地参与卵黄粒形成。卵周隙内的外源性物质有两个来源:滤泡细胞的合成产物和血淋巴携带、转运的卵黄蛋白前体物。这些外源性物质主要通过质膜的微吞饮作用和微绒毛的吸收作用这两种方式进入卵母细胞,进而形成外源性卵黄。内源性和外源性的卵黄物质共同参与成熟卵母细胞中富含髓样小体的卵黄粒的形成。卵壳的形成和微绒毛的回缩被认为是东方扁虾卵母细胞成熟的形态学标志。     

东方杯叶吸虫卵黄腺和卵巢的超微结构研究

本文应用透射电镜观察了东方杯叶吸虫卵黄腺和卵巢的超微结构,并与体外培养成虫进行比较。根据形态特征和内含物的存在情况,将卵黄细胞和卵母细胞的发育均分为不同时期,详细描述了各期的形态特征,探讨了卵黄球和皮质颗粒等内含物的生理功能。体外培养成虫成熟卵黄细胞中有散在的卵黄物质,成熟卵母细胞中线粒体囊泡化,这些可作为体外培养的评价指标。     

中华稻蝗卵子卵黄发生期超微结构研究

利用透射电镜研究了中华稻蝗Oxya chinesis卵子发生中卵黄发生期的超微结构.卯黄发生初期,滤泡上皮细胞胞质内出现大量粗面内质网及线粒体等细胞器,可能与为卵母细胞提供营养有关.卵黄发生期卵母细胞胞质内卵黄球逐渐增多,它也许有多种来源.观察到环形片层结构,并讨论了其可能功能.     

西瓜不同发育时期的助细胞超微结构的变化（简报）

The ultrastructure of synergids of watermelon (Citrullus Lanatus L.) was investigated using transmission electron microscopy at following stages of embryo sacs: 1. Unpollination, on the first flowering day. 2. Unpollination, on 2nd day after anthesis (DAA). 3. Fertilization, on DAA 2. The synergids with distinct filiform apparatus at the micropylar end have abundant organelle, such as mitochondria, endoplasmic reticulum, and plastids in cytoplasm, which indicate that they are active on the first flowering day. No wall is present at the chalazal part of synergid, and there are some flocculent materials and vesicles in the spaces of cytoplasma membranes among synergid, egg cell and central cell in embryo sacs at the first and the second stages. On DAA 2, in unpollinated embryo sacs, the central large vacuole of synergid is divided into several smaller ones and the starch grains decrease in cytoplasm. There is no newly synthesized wall at the chalazal end of persistent synergid in fertilized embryo sacs. The contents of degenerated synergid, in the form of electron dense granules, are located in the wide space among central cell, zygote and persistent synergid, and some of them migrate into central cell through cytoplasma membrane. Therefore, it is deduced that the contents of synergid might serve as a nutrient supplement to the development of endosperm, but not embryo.     

凡纳滨对虾卵母细胞卵黄发生的超微结构

利用电镜研究凡纳滨对虾卵母细胞卵黄发生的全过程。结果表明 :凡纳滨对虾卵黄的发生是双源性的。卵黄发生早、中期是内源性卵黄大量合成的阶段 ,卵黄发生中、后期则以外源性卵黄的合成为主。内源性卵黄主要由内质网、线粒体、核糖体、溶酶体、高尔基器等多种胞器活跃参与形成。其中数量众多的囊泡状粗面内质网是形成内源性卵黄粒的最主要的细胞器 ;部分线粒体参与卵黄粒的合成并自身最终演变为卵黄粒 ;丰富的游离核糖体合成了大量致密的蛋白质颗粒并在卵质中直接聚集融合成无膜的卵黄粒 ;溶酶体通过吞噬、消化内含物来形成卵黄粒和脂滴 ,且方式多样 ;高尔基器不直接参与形成卵黄粒。外源性卵黄主要通过卵质膜的微吞饮活动从卵周隙或卵泡细胞中摄取外源物质来形成     

栽培甜菜花粉发育过程的超微结构

利用透射电镜技术对栽培甜菜（Beta vuigaris）花粉发育过程进行了超微结构观察。结果表明,在小孢子母细胞减数分裂期间,细胞内发生了“细胞质改组”,主要表现在核糖体减少,质体和线粒体结构发生了规律性变化。末期1不形成细胞板,而是在2个子核间形成“细胞器带”。“细胞器带”的存在起到类似细胞板的作用,暂时将细胞质分隔成两部分。四分体呈四面体型,被胼胝质壁包围。小孢子外壁的沉积始于四分体晚期,至小孢子晚期外壁已基本发育完全。单核小孢子时期,细胞核大,细胞器丰富。二细胞花粉发育主要表现在生殖细胞壁的变化上,生殖细胞壁上不具有胞间连丝。成熟花粉为三细胞型,含有1个营养细胞和2个精细胞。精细胞具有短尾突,无壁,为裸细胞,每个精细胞通过2层质膜与营养细胞的细胞质分开。生殖细胞与精细胞里缺乏质体。     

栽培甜菜花粉发育过程的超微结构

利用透射电镜技术对栽培甜菜(Beta vulgaris)花粉发育过程进行了超微结构观察。结果表明, 在小孢子母细胞减数分裂期间, 细胞内发生了“细胞质改组”, 主要表现在核糖体减少, 质体和线粒体结构发生了规律性变化。末期I 不形成细胞板,而是在2个子核间形成“细胞器带”。“细胞器带”的存在起到类似细胞板的作用, 暂时将细胞质分隔成两部分。四分体呈四面体型, 被胼胝质壁包围。小孢子外壁的沉积始于四分体晚期, 至小孢子晚期外壁已基本发育完全。单核小孢子时期, 细胞核大, 细胞器丰富。二细胞花粉发育主要表现在生殖细胞壁的变化上, 生殖细胞壁上不具有胞间连丝。成熟花粉为三细胞型, 含有1个营养细胞和2个精细胞。精细胞具有短尾突, 无壁, 为裸细胞, 每个精细胞通过2层质膜与营养细胞的细胞质分开。生殖细胞与精细胞里缺乏质体。     

泥螺卵黄发生过程中线粒体的变化

利用透射电镜（TEM）技术研究了泥螺卵黄发生过程中线粒体的形态结构的变化特点,结果表明,从卵黄发生早期到晚期,卵母细胞内线粒体经历了从外部形态到内部结构的一系列变化。卵黄合成初期的卵母细胞内,线粒体多,结构典型,仅部分线粒体外膜破裂,嵴 和内膜逐渐消失,卵黄发生中期,线粒体基质空泡化,嵴和内膜消失,腔内充满颗粒状物质,最后演变成卵黄颗粒,随着卵母细胞的发育,卵黄颗粒的数量和直径逐渐增加,卵黄发生后期,卵质中胞器不发达,细胞质中充满卵黄颗粒,在卵黄颗粒之间仅有少量线粒体存在,提供细胞代谢所需的能量,此外,对线粒体在卵黄形成中的功能,去向及行为变化等 进行了讨论。     

Ultrastructure of vitellogenesis and vitellocytes in the trypanorhynch cestode Aporhynchus menezesi, a parasite of the velvet belly lanternshark Etmopterus spinax

This is the first TEM examination of vitellogenesis in the cestode Aporhynchus menezesi, a parasite of the velvet belly lanternshark Etmopterus spinax and a member of a little-studied trypanorhynch family, the Aporhynchidae. The synthetic activity of vitellocytes plays two important functions in the developmental biology of cestodes: (1) their shell-globules serve in eggshell formation; and (2) their accumulated reserves of glycogen and lipids represent a food source for the developing embryo. In A. menezesi, vitelline follicles consist of cells at various stages of development, from peripheral, immature cells of the gonial type to mature cells towards the centre of the follicle. These stages are: (I) immature; (II) early differentiation; (III) advanced maturation; and (IV) mature. Gradual changes involved in this process occur within each stage. Vitellogenesis involves: (1) an increase in cell volume; (2) the development of a smooth endoplasmic reticulum and an accelerated formation and accumulation of both unsaturated and saturated lipid droplets, along with their continuous enlargement and fusion; (3) the formation of individual β-glycogen particles and their accumulation in the form of glycogen islands scattered among lipid droplets in the cytoplasm of maturing and mature vitellocytes; (4) the rapid accumulation of large, moderately saturated lipid droplets accompanied by dense accumulations of β-glycogen along with proteinaceous shell-globules or shell-globule clusters in the peripheral layer during the advanced stage of maturation; (5) the development of cisternae of granular endoplasmic reticulum that produce dense, proteinaceous shell-globules; (6) the development of Golgi complexes engaged in the packaging of this material; and (7) the progressive and continuous enlargement of shell-globules into very large clusters in the peripheral layer during the advanced stage of maturation. Vitellogenesis in A. menezesi, only to some extent, resembles that previously described for four other trypanorhynchs. It differs in: (i) the reversed order of secretory activities in the differentiating vitellocytes, namely the accumulation of large lipid droplets accompanied by glycogenesis or β-glycogen formation during early differentiation (stage II), i.e. before the secretory activity, which is predominantly protein synthesis for shell-globule formation (stage III); (ii) the very heavy accumulation of large lipid droplets during the final stage of cytodifferentiation (stage IV); and (iii) the small number of β-glycogen particles present in mature vitellocytes. Ultracytochemical staining with PA-TCH-SP for glycogen proved positive for a small number of β-glycogen particles in differentiating and mature vitellocytes. Hypotheses, concerning the interrelationships of patterns of vitellogenesis, possible modes of egg formation, embryonic development and life-cycles, are commented upon.     

Morphological characterization of the ovary and oocytes vitellogenesis of the tick Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae)

This study presents the morphology of the ovary, as well as the process of the vitellogenesis in oocytes of the tick Rhipicephalus sanguineus. The ovary of these individuals is of the panoistic type; therefore, it lacks nurse cells. This organ consists of a single tubular structure, continuous, and composed of a wall formed by small epithelial cells with rounded nuclei which delimit the lumen. The oocytes in the different developmental stages in this tick species were classified into five stages (I-V). They remain attached to the ovary during vitellogenesis by a cellular pedicel and afterwards the mature oocytes (stage V) are released into the ovary lumen.     

Calmodulin transmitted through gap junctions stimulates endocytic incorporation of yolk precursors in insect oocytes

In ovarian follicles of Oncopeltus fasciatus, and of Xylocopa virginica, calmodulin (CaM) of epithelial cell origin is required by oocytes for endocytic uptake of yolk precursor molecules. Furthermore, this 17-19 kDa protein is normally transported to the oocytes via gap junctions. Downregulation of gap junctions by treatment with 1 mM octanol or separation of the epithelial cells from their oocytes terminated precursor uptake, and this activity could be rescued by microinjection of 60 microM CaM, but not by injections of incubation medium, nor solutions of other molecular species tested. That endogenous CaM is required was confirmed by incubating otherwise untreated follicles in physiological salt solution (PSS) containing either calmidazolium or W-7, both known antagonists of CaM. By radioimmunoprecipitation, we show that the epithelial cells surrounding an oocyte synthesized 15 times as much calmodulin as did the oocytes they encircled. Neither octanol-treated follicles nor denuded oocytes incubated in medium containing calmodulin were able to resume endocytosis, arguing against an extracellular route. However, fluorescently labeled calmodulin microinjected into oocytes is shown to have crossed through gap junctions, making epithelial cells distinctly fluorescent.     

Spawning behaviour of taimen (<Emphasis Type="Italic">Hucho taimen</Emphasis>) from the Uur River,Northern Mongolia

This study presents the first observations of Hucho taimen spawning in the wild based on underwater video recordings. One pair of taimen was monitored during a 19 h period, supplemented with visual observations from two other spawning pairs. We recorded two full spawning events performed in two different locations separated by approximately 30 m. The absence of an established male hierarchy along a nesting female was the most important difference between taimen and other salmonine breeding biology. Taimen spawning, based on our observations, is a single pair event. The male prevented the approach of other males by launching intense attacks that extended for several meters away from the redd. Our data suggests that taimen females, differently from other salmonines, do not cover their eggs immediately after having spawned but rest for a variable number of minutes before covering them.     

An Endoreticulatus species from Ocinara lida (Lepidoptera: Bombycidae) in Taiwan

A microsporidium from the Ficus pest, Ocinara lida, in Taiwan is characterized. The taxonomic position of this species was preliminarily determined by sequencing small subunit rRNA gene (SSUrRNA). Analysis of the SSUrRNA sequence indicated that this isolate from O. lida is a member of the genus Endoreticulatus and belongs to the genetic grouping containing other lepidopteran Endoreticulatus species we have analyzed phylogenetically. The taxonomic position of this isolate was also confirmed by the ultrastructural characteristics of this isolate. The congruence between SSUrRNA sequence analysis and ultrastructural characteristics shows that this isolate is more closely related to Endoreticulatus bombycis than to Endoreticulatus schubergi Zw?lfer.     

Amblyomma triste (Koch, 1844) (Acari: Ixodidae): morphological description of the ovary and of vitellogenesis

The present study presents the morphology, histology, and the dynamics of vitellogenesis in females of the tick Amblyomma triste. The ovary in this species is of the panoistic type, therefore it lacks nurse cells. It is composed of a layer of epithelial cells that outwardly form the wall of the ovary, but also originate the pedicel, the structure that attaches the oocytes to its external margin, as well the oocytes themselves. In Amblyomma triste, the oocytes develop in four synchronic stages, which differs from the process in other tick species. The classification of the stages of the oocytes was carried out based on the presence of four morphologic characteristics: cytoplasm appearance; site of the germ vesicle; presence, quantity, and constitution of the yolk granules and presence of chorium.     

Cladochytriales—a new order in Chytridiomycota

Recently, molecular and ultrastructural analyses have resulted in revised phylogenetic hypotheses in the phylum Chytridiomycota. The order Chytridiales, once considered monophyletic, has been subdivided into several new orders. However, the most recent analyses indicate that the emended Chytridiales is also polyphyletic. One monophyletic lineage in Chytridiales includes Cladochytrium, Nowakowskiella, and five other genera. Many of the chytrids in this clade have often been observed growing on decaying plant tissue and other cellulosic substrates from aquatic habitats and moist soils. In this study we analysed combined nu-rRNA gene sequences (partial SSU and LSU) of 30 isolates from North American aquatic and soil samples. Based on molecular monophyly and zoospore ultrastructure, we designate this clade as a new order, Cladochytriales, which includes four families: Cladochytriaceae, Nowakowskiellaceae, Septochytriaceae fam. nov., and Endochytriaceae.     

Fat body cells of Amblyomma cajennense partially engorged females (Acari: Ixodidae) and their role on vitellogenesis process

During the process of Arthropoda reproduction, the synthesis and uptake of proteins, carbohydrates, and lipids by oocytes is termed vitellogenesis. These compounds that will make up the yolk may be in ticks endogenously synthesized by the oocytes and/or exogenously produced by the fat body and pedicel cells. This study examined the fat body of Amblyomma cajennense ticks at the cytochemical ultrastructural level to demonstrate the presence of lipids, proteins and carbohydrates in trophocytes. The lipids were detected in higher quantity than proteins and carbohydrates in the fat body cells, suggesting that the role of the fat body in tick is stored lipids and carbohydrates to convert them in energy, or still they could be used with cell structural purpose. The electrophoresis technique applied at A. cajennense fat body demonstrated specifically the molecular mass of proteins: about 98 kDa. By the other hands, the fat body is not the organ responsible for the synthesis of the yolk protein, role probably performed by the pedicel cells.