蕨类植物分株紫萁精子发生过程中生毛体和多层结构的超微结构

应用电镜技术对蕨类植物分株紫萁(Osmunda cinnamomea L. var．asiatica Fernald)精子发育过程中的生毛体和多层结构的超微结构进行了研究。牛毛体在幼精了细胞中出现,正在分化的生毛体略呈球状,球状体的中央由一团染色深的颗粒状物质构成,外围分化出若干柱状体。已分化的生毛体由柱状体分散或辐射状排列构成,呈球状,球体中心不含染色深的物质。多层结构位于精子细胞内的基体和巨大线粒体之间,刚形成时仅由片层构成,片层相互平行排列形成片层带。多层结构在分化中期由微管带、片层带和蚀斑三层构成。多层结构在分化末期又形成附属微管带、嗜锇冠和嗜锇层。微管带从多层结构长出,沿细胞核的表面伸展,并与核膜之间形成复合结构。基体由柱状体转变而成,它向两端生长,在远端产生鞭毛的轴丝,在近轴端形成楔状结构。本文首次详细阐明了原始薄囊蕨分株紫其生毛体和多层结构发育的超微结构特点,并与其他蕨类进行了比较,发现其片层带出现在微管带形成之前。     

蕨类植物精细胞运动器和细胞骨架的研究

介绍了近年来蕨类植物游动精子运动器和细胞骨架的研究进展.游动精子由配子体精子器中的非运动细胞发育形成,其分化过程包括了运动器官和细胞骨架的合成和组装.精子发生过程中形成的运动器的各部分结构包括鞭毛、基体、多层结构及附属结构;基体是细胞中新形成的结构,在不同类群的蕨类植物中分别由双中心粒、分支生毛体和生毛体产生.鞭毛、基体和多层结构中的微管带形成了游动精子三个独特的微管列阵,由于微管蛋白的后修饰作用这些微管列阵十分稳定;centrin是运动器中的重要成分,但功能尚不清楚,可能和细胞骨架及运动器的构建有关.     

蕨类植物精细胞运动器和细胞骨架的研究

介绍了近年来蕨类植物游动精子运动器和细胞骨架的研究进展。游动精子由配子体精子器中的非运动细胞发育形成,其分化过程包括了运动器官和细胞骨架的合成和组装。精子发生过程中形成的运动器的各部分结构包括鞭毛、基体、多层结构及附属结构;基体是细胞中新形成的结构,在不同类群的蕨类植物中分别由双中心粒、分支生毛体和生毛体产生。鞭毛、基体和多层结构中的微管带形成了游动精子三个独特的微管列阵,由于微管蛋白的后修饰作用这些微管列阵十分稳定;centrin是运动器中的重要成分, 但功能尚不清楚,可能和细胞骨架及运动器的构建有关。     

傅氏凤尾蕨精子发生超微结构的研究

超微结构研究显示傅氏凤尾蕨（Pteris fauriei Hieron）精子发生过程包括生毛体、多层结构和鞭毛等运动细胞器重新发生,环状线粒体形成,核塑形等过程,最后形成一个螺旋形的游动精子,这与其他真蕨类精子发生过程相似。本研究观察到的一些新现象包括：精细胞在分化早期呈极性,细胞核位于精细胞的近极端,生毛体、线粒体和质体等细胞器主要分布远极端;在生毛体分化早期,可见大量微管从其发出,其周围线粒体丰富;基体分化经历了前中心粒、中心粒和基体3个阶段,它们的内部结构不同;研究表明生毛体内的不定形物质是微管组织者,多层结构、附属微管带及鞭毛等细胞器均由不定形物质分化形成;精细胞在分化过程中产生了丰富的膜结构,它们可能为精核塑形提供原料。本研究报道了傅氏凤尾蕨精细胞分化的一些细节,这有助于进一步揭示蕨类植物精子发生的细胞学机制。     

银杏精子细胞生毛体及其它细胞器的超微结构

生毛体与嗜锇颗粒是银杏 (Ginkgobiloba)精子细胞中最具有标志性的结构。生毛体是细胞质内一直径为 3～ 4μm的圆球形结构 ,它由一个电子致密的核心和由此向周边发散出的辐射状中心粒组成 ,致密核心上具有微管结构的弱电子染色区域 ,并有微管从生毛体延伸到细胞质。嗜锇颗粒直径为 1 0～ 2 0μm,呈圆球状 ,位于生毛体和细胞核之间 ,其相对的另一侧存在纤维颗粒体。在精子细胞质内 ,特别是嗜锇颗粒和生毛体周围线粒体、质体、内质网、高尔基体等细胞器丰富。银杏精子细胞核较大 ,在细胞核内 ,核仁结构呈球形 ,电子染色致密的颗粒区在周围 ,而纤维组分则在圆球的中间。在核膜表面布满了分布不均匀的核孔复合体。     

海金沙精细胞中生毛体发育及多层结构起源的超微结构研究

蕨类植物海金沙（LygodiumJaponicum（Thunb．）Sw．）的游动精子发育过程中,生毛体在精母细胞的细胞质中出现,它是直径为0．5－0．6μm的椭球体,其结构紧密,由辐射排列的具轮辐结构的管状亚单位和无定形基质组成。大量微管从生毛体伸向细胞质。随着精细胞的发育,生毛体结构变得松散,亚单位分化形成的中心粒彼此分开扩散到外围,中心为无定形物质。伴随着中心粒的分化,多层结构出现,一端与无定形基质相连。多层结构由外侧的微管带及内侧的片层组成,形成后与一线粒体相连,移向靠近核的位置,并正对着核上出现凹点。研究发现在精原细胞后期出现一团絮状结构,为无定形基质,其中有深染色的小管状结构分布,同时可见微管从絮状结构边缘伸出,这一絮状结构可能与生毛体的产生有一定的关系。     

绵马鳞毛蕨精母细胞和游动精子超微结构特征的研究

应用电镜技术对蕨类植物绵马鳞毛蕨(RYOPTERIS CRASSIRHIZOMA Nakai)精母细胞和游动精子的超微结构特征进行了研究。精母细胞为多边形,细胞质内含有丰富的线粒体、质体、内质网、高尔基体等常见的细胞器．在细胞质中还可见到一些同心圆膜状结构,位于质膜的附近或精母细胞的角偶。同心圆膜状结构由双层膜环绕构成,外被l层单位膜。精母细胞与精子器的璧细胞之间形成了分离腔。在精母细胞质膜外形成了嗜锇层,这些结构的形成说明精母细胞已经开始与雄配子体逐渐分离,进入独立发育的阶段。尽管精母细胞之间也有嗜锇层的形成,但嗜锇层是不连续的,其上有一些空隙,精母细胞之间可通过空隙进行物质和信息的交流。成熟的精子细胞外被l层透明的薄膜,里面为游动精子。螺旋状。由环状细胞器环绕3～4圈构成．这些环状细胞器包括多层结卡构、微管带、巨大线粒体、鞭毛带和1个长形浓缩的细胞核。游动精子的后端为一些泡囊化的细胞质．其中包括一些残存的线粒体、造粉质体及大的囊泡等。当成熟的精子细胞排出精子器后。其内的游动精子挣脱透明质膜的束缚,摆脱后端的囊泡,成为1条游动精子。本文还对绵马鳞毛蕨和其它蕨类植物精子的超微结构特征进行了比较。     

水蕨卵膜的形成及其超微结构的观察

蕨类植物成熟卵的周围有一层卵膜,但其细微结构和形成过程仍不清楚,本研究应用透射电镜技术对水蕨(Ceratopteris thailictroides)卵细胞发育过程中卵膜的形成及超微结构进行了观察.结果表明水蕨卵细胞在发育中期开始形成卵膜,卵上方的卵膜十分显著,是由多层嗜锇性内质网片层附着于质膜内表面形成的,成熟时卵上方的卵膜中心部分厚,向边缘逐渐变薄,在嗜锇性片层之间填充有嗜锇性物质.比较而言,卵下方及侧面的卵膜薄,由两层紧密连接的嗜锇性膜构成.首次阐明了蕨类植物卵膜形成的超微结构,并对卵膜的一些功能进行了探讨.     

水蕨精子发生过程中中心体蛋白和微管蛋白的免疫荧光定位

采用透射电镜技术和免疫荧光标记技术对水蕨精子发生的超微结构以及中心体蛋白和微管蛋白在精子发生过程中的动态表达进行了观察。研究发现：（1）生毛体分化早期周围有放射状微管分布,这与线粒体向生毛体的聚集有关。（2）免疫荧光观察表明,中心体蛋白仅定位于生毛体、基体和鞭毛带上,自生毛体至基体阶段呈现明亮的荧光标记,在核塑形、鞭毛形成至精子成熟阶段,中心体蛋白荧光标记随着鞭毛的发生而逐渐减弱,至游动精子阶段中心体蛋白荧光标记信号几乎消失。（3）微管蛋白早期荧光标记与中心体蛋白标记形相同,在生毛体、鞭毛带、基体等运动细胞器上呈现明亮荧光标记,但微管蛋白随着鞭毛的发生其荧光标记越来越强。从二者的时空表达特征可以推断,中心体蛋白主要是运动细胞器的组织者,而非这些运动细胞器的结构成分,其功能是参与或负责中心粒、基体和鞭毛的发生。     

海金沙精细胸中生毛体发育及多层细胞起源的超微结构研究

蕨类植物海金沙（Ｌｙｇｏｄｉｕｍ ｊｏｐｏｎｉｃｕｍ （Ｔｈｕｎｂ．）Ｓｗ．）的游动精子发育过程中,生毛体在精母细胞质中出现,它是直径为０．５～０．６μｍ的椭球,其结构紧密,由辐射排列的具轮辐结构的管状亚单位和无定形基质组成。大量微管从生毛体伸向细胞质。随着精细胞的发育,生毛体细胞变得松散,亚单位分化形成的中心粒彼此分开矿散到外围,中心为无定形物质。伴随着中心粒的分化,多层结构出现,一端与无定形基     

ULTRASTRUCTURAL STUDIES OF SPERMATOGENESIS IN THE ANTHOCEROTALES. I. THE BLEPHAROPLAST AND ANTERIOR MITOCHONDRION IN PHAEOCEROS LAEVIS: EARLY DEVELOPMENT

Electron microscopic examination of thin sections showed that the blepharoplast of a young spermatid of Phaeoceros consists of two side-by-side centrioles and an accumulation of osmiophilic, granular matrix at their proximal ends. Lying between these nearly parallel organelles is a dark-staining body that will later disappear at the onset of flagellogenesis. For a brief period the centrioles are oriented perpendicular to the nuclear surface so that the granular matrix at their proximal ends is confluent with the nuclear envelope; furthermore, the nucleoplasm immediately in front of the centrioles becomes densely staining. The multilayered structure (MLS) develops directly under the centrioles. It comprises a band of 12 microtubules (the S₁ stratum) and three lower strata (S_2–4) whose constitutent lamellae are oriented at an oblique angle to the S₁ axis. While the S₁ tubules grow rearward over the nucleus which forms a beak adjacent to the posterior end of the lamellar strata, the centrioles are transformed into basal bodies with the distal growth of the axonemes and the proximal growth of the central cartwheels and lowermost triplets. The proximal ends of the basal bodies and the S₁ tubules overlying the lamellar strata are invested with osmiophilic matrix that extends down to the S₂ layer and may temporarily occlude the lamellar plates. At the onset of nuclear elongation an anterior mitochondrion becomes situated close beneath the lamellar strata which extend laterally beyond the S₁ tubules.     

分株紫萁卵发生的超微结构

用透射电镜对蕨类植物分枝紫其(Osmunda cinnamamae L. var.asiatica Fernald)卵发生进行了超微结构的研究.卵发生过程中,许多泡囊不仅移向细胞周围,而且在细胞质膜内排为一列,并通过胞吐作用聚集在细胞质膜外,它们释放或分泌嗜锇物质.观察到少数泡囊内含片层状结构的嗜饿物质紧贴于细胞质膜,似乎将其冲破.与此同时,在卵细胞和颈卵器壁之间形成分离腔,其宽度大于以往报道的真蕨类,在卵细胞质膜外出现额外的卵膜,其宽度大于蕨属和鳞毛蕨属.造粉体被大型常呈三角状半圆形或近椭圆形的淀粉粒所充满,当卵成熟时逐渐减少.核大型平扁状,核内出现2~3对平行的双层膜,紧贴核膜.未发现核外突.线粒体一度似不发育,最后恢复正常.     

分株紫萁卵发生的超微结构

用透射电镜对蕨类植物分枝紫萁(Osmunda cinnamamae L. var. asiatica Fernald)卵发牛进行了超微结构的研究。卵发生过程中,许多泡囊不仅移向细胞周围,而且在细胞质膜内排为一列,并通过胞吐作用聚集在细胞质膜外,它们释放或分泌嗜锇物质。观察到少数泡囊内含片层状结构的嗜饿物质紧贴于细胞质膜,似乎将其冲破。与此同时,在卵细胞和颈卵器壁之问形成分离腔,其宽度大于以往报道的真蕨类,在卵细胞质膜外出现额外的卵膜,其宽度大于蕨属和鳞毛蕨属。造粉体被大型常呈三角状半圆形或近椭圆形的淀粉粒所充满,当卵成熟时逐渐减少。核大型平扁状,核内出现2-3对平行的双层膜,紧贴核膜。未发现核外突。线粒体一度似不发育,最后恢复正常。     

Ultrastructure of Blepharoplast and Other Organelles of the Spermatid in Ginkgo biloba

Both blepbaroplast and osmiophilic globule were characteristic structures to the spermatid of Ginkgo biloba. The blepharoplast of Ginkgo biloba ranged from 3 ～ 4 μm in diameter and consisted of a number of basal centrioles radiating from an electron dense core that contained electron-lucent areas with microtubule structure. Microtubules extended radially from the blepharoplast into the cytoplasm. A large round osmiopbilie globule with a diameter of about 10～20/μm, was located between the blepharoplast and the nucleus, while a filbrillogranular body in the cytoplasm was opposite to the osmiophilic globule. There were numerous mitochondria, plastids, endoplasmic reticulia and dictiosomes in the cytoplasm, particularly around the blepharoplast and the osmiophilic globule of sperm cells. The nucleus of spermatid in Ginkgo biloba was large and roundly elliptical in shape. The large spheroidal nucleolus was the most obvious structure in the nucleus, There were two regions in the nucleolus distinguished by TEM: A ring-shaped granular component, which contained maturing ribosomal precursor particles; and a centrally placed fibrillar component. The nuclear pore complexes in the nuclear envelope were plentiful but not evenly distributed.     

STUDIES OF SPERMATOGENESIS IN THE HEPATICAE V. BLEPHAROPLAST DEVELOPMENT IN MARCHANTIA POLYMORPHA

Coaxial centrioles and a microtubule organizing center (MTOC) constitute each centrosome in spermatid mother cells of Marchantia polymorpha. During cell division the centrosome separates at its midregion and the two centrioles undergo a planar rotation that brings them to lie somewhat staggered and nearly parallel with their proximal ends embedded in osmiophilic granular material similar in appearance to that of the MTOC. Microtubules of the multilayered structure (MLS) arise in this material below the posterior centriole and parallel to its long axis. The rotation of centrioles and the initiation of S₁ tubules below the posterior centriole determine polarity of the incipient blepharoplast. Lower MLS strata are formed under the anterior centriole by the compaction of granular, osmiophilic matrix. Formation and growth of S₂ vertical lamellae occur at the left front edge of the MLS in association with MTOC-like matrix localized near the cell membrane. The MLS enlarges to about 0.4 μm wide by 0.6 μm long and is ovoid in outline except for a short distal projection underlying the posterior centriole. Subsequently the lamellae are transformed into homogenous, osmiophilic matrix that contributes directly to the expansion of all MLS strata including microtubules. The stratum of lamellae is interpreted as a planar MTOC subject to morphogenetic control. Each of the four strata grows proximally while the tapering distal projection lengthens beneath the posterior basal body. Dense matrix above the MLS, apparently elaborated by the S₂ layer, is organized into cartwheel and triplet components of the basal bodies’ proximal extensions. Organization of triplet tubules proceeds from proximal to distal toward preexisting triplets. Osmiophilic matrix contributes to the formation of microtubule keels and osmiophilic crests and may serve as a cementing material that stabilizes the spatial relationships of blepharoplast components. After full expansion of the MLS’ lower strata, the S₂ layer is reorganized into lamellae. Flagellar growth in Marchantia is postulated to involve a process whereby subunits or their precursors are elaborated by the MLS, translocated to the distal end of the flagellum and incorporated into the axonemal tubules. When MLS microtubules elongate to form a long, narrow band, the distal half of the S₂ layer is again in the osmiophilic matrix state.     

Ultrastructural characterization of the locomotory cytoskeletal system of the spermatozoid inGinkgo biloba

Summary The development of the locomotory cytoskeletal system of sperm is carefully coordinated with the development of the sperm inGinkgo biloba. Here we report further ultrastructural characterization of the locomotory cytoskeletal system in the developing spermatid and mature spermatozoid, particularly with respect to the initiation and early development of the flagellar apparatus. A multilayered structure (MLS) assembles from an electron-dense matrix that self-organizes after blepharoplast breakup and then further elongates. At the tail of the assembling MLS, the spline microtubules connect to an anterior beak of the nuclear envelope. Nuclear-pore complexes are found on the nuclear envelope close to this beak. The mitochondria which elongate and line up one behind the other are tightly associated with the MLS. The MLS ofG. biloba is composed of an upper layer of parallel spline microtubules and a lower layer consisting of a fibrous lamellar strip composed of paralled fibers about 9 nm in diameter. Higher-magnification images show that the fully assembled fibers of the lamellar strip consist of subunits which suggest that protofilaments are involved in the assembly processes. A unique cytoskeletal system of the spermatozoid inG. biloba is given by the anterior bundle of microtubules. This bundle, in which microtubules are arranged parallel to each other, forms between the plasmalemma and the MLS and is about 214–392 nm in cross section. These microtubules expand spirally along the MLS band. Other details of cellular fine structure of the mature spermatozoid are described.     

SPERMATOGENESIS IN A HOMOSPOROUS FERN,ONOCLEA SENSIBILIS

A detailed study of spermatogenesis in a homosporous fern, Onoclea sensibilis L., is presented from the formation of the first spermatogenous cell to the release of the sperm. Two different walls are deposited around the developing spermatids at specific developmental stages as opposed to one wall reported for other species. Most ultrastructural changes that occur in Onoclea during spermatid differentiation resemble those described in previous studies on other fern species, with the following exceptions: 1) A previously undescribed structure appears during midspermatid stage. This dense layer of amorphous material with a row of evenly spaced light areas occurs between the anterior portion of the mitochondrion associated with the multilayered structure and the anterior plasmalemma of the spermatid. 2) An early stage in blepharoplast formation resembles that which occurs in the heterosporous fern Marsilea, in contrast to that which has been reported in Platyzoma, the only other homosporous fern studied at this stage. 3) The osmiophilic crest does not form as early as reported in other ferns. 4) The cap cell of Onoclea is removed intact, rather than collapsing or forming a pore during sperm release. Observations are reported on the number of sperm per antheridium, the time course of spermatogenous cell mitosis, and of differentiation of spermatids into sperm. In Onoclea, an antheridium may contain either 32 or 64 sperm. Regardless of the final number of sperm, each has approximately the same volume.     

CENTRIOLE REPLICATION : II. Sperm Formation in the Fern, Marsilea, and the Cycad, Zamia

Sperm formation was studied in the fern, Marsilea, and the cycad, Zamia, with particular emphasis on the centrioles. In Marsilea, the mature sperm possesses over 100 flagella, the basal bodies of which have the typical cylindrical structure of centrioles. Earlier observations by light microscopy suggested that these centrioles arise by fragmentation of a body known as the blepharoplast. In the youngest spermatids the blepharoplast is a hollow sphere approximately 0.8 µ in diameter. Its wall consists of closely packed immature centrioles, or procentrioles. The procentrioles are short cylinders which progressively lengthen during differentiation of the spermatid. At the same time they migrate to the surface of the cell, where each of them puts out a flagellum. A blepharoplast is found at each pole of the spindle during the last antheridial mitosis, and two blepharoplasts are found in the cytoplasm before this mitosis. Blepharoplasts are also found in the preceding cell generation, but their ultimate origin is obscure. Before the last mitosis the blepharoplasts are solid, consisting of a cluster of radially arranged tubules which bear some structural similarity to centrioles. In Zamia, similar stages are found during sperm formation, although here the number of flagella on each sperm is close to 20,000 and the blepharoplast measures about 10 µ in diameter. These observations are discussed in relation to theories of centriole replication.