三疣梭子蟹活体胚胎发育的观察

观察了三２梭子蟹胚胎发育全过程。整个胚胎发育过程约需６８０小时。孵排出约５２小时后开始表面孵裂,至２５６细胞时进入囊胚期。囊胚后期,预定内胚层细胞出现,并与集中在其周围的 起内陷,形成原肠。     

简述两栖类的原肠作用及三胚层形成

在讲到动物发育时,常遇到一个不易理解和讲述的动态过程,就是蛙胚的原肠发生过程及三胚层的形成。原肠胚是胚胎发育中一个极为重要的时期,胚胎从囊胚未分化的分裂球发育成为具有内、中、外三个胚层的原肠胚,并将决定其各器官原基,它是通过空间和时间方面的紧密结合,复杂的形态发生运动而完成的。内胚层形成消化道     

四刺泡角跳（Ceratophysella duplicispinosa）个体发育的初步研究

描述了北方菜园优势跳虫四刺泡角跳（Ceratophysella duplicispinosa）的胚胎发育及胚后发育过程。结果表明：①四刺泡角跳为聚产卵,每窝卵数22-53粒,卵粒D=220μm。②其胚胎发育历时约8．3d（200h）,行完全均等卵裂,以内陷方式形成二胚层;③组织器官分化早期背面中部出现凹陷,成为头部与胸腹部最早的界限,同时在腹面出现附肢原基;④无体节幼虫期的触角、口器、足、腹管、弹器及腹部尾叶等器官都以附肢原基的形式出现,至孵化前期显现出各器官形态：出壳前3d开始出现一对红色眼斑。⑤胚后发育（自孵化出壳至首次产卵）历时29d,体色先后为白色（初孵化幼体）、棕红至灰色（亚成体）、紫黑色（成体）。     

施氏獭蛤融合卯裂及其胚胎发育过程观察

对施氏獭蛤胚胎发育过程进行了观察,结果显示:(1)与其他双壳类相似,施氏獭蛤胚胎发育过程可以分为卵裂期、囊胚期、原肠期、担轮幼虫期和面盘幼虫期;(2)在卵裂阶段,施氏獭蛤的卵裂方式完全不同于其他动物;施氏獭蛤卵子发育到第一次成熟分裂前期(胚泡破裂前)即有受精能力,但卵子受精后未观察到极体排出的现象,而是有多核受精卵产生;在以后的卵裂过程中,受精卵没有进行其他动物的经裂或纬裂,而是以一种独特的、复杂的分裂方式--融合卵裂进行卵裂,即:二细胞、叫细胞、八细胞进行下一次卵裂之前,细胞核逐渐消失,分裂球逐渐融合成一个细胞,一段时间后在细胞中央逐渐出现数量加倍的细胞核,细胞核逐渐向外周移动,最后一次性地分裂出数量加倍的分裂球.     

远海梭子蟹胚胎发育观察

在水温25～26℃、盐度30和pH 7.8～8.4条件下,观察远海梭子蟹胚胎发育全过程,其结果发现,远海梭子蟹胚胎发育经历卵裂、囊胚、原肠胚、无节幼体、后无节幼体和原溞状幼体等六个阶段.远海梭子蟹卵排出约28h开始表面卵裂,约40h,形成囊胚,约60h,预定内胚层细胞出现,并与集中在其周围的细胞一起内陷,形成原肠胚.约90h,3对附肢的无节幼体出现,约110h,5对附肢的后无节幼体出现,约140h,7对附肢的原溞状幼体出现.复眼、心跳、色素形成均在原潘状幼体阶段完成.原溞状幼体孵出时(约300h),颚足长出羽状刚毛,变为溞状幼体.整个胚胎发育过程约300h.     

人体胚胎发育概况与新进展（二）：人胚早期发育

第1—8周是人胚早期发育阶段,又称胚期。在这个时期,受精卵经过分裂,增殖和分化,形成桑椹胚、胚泡,进而分化形成内、中、外三胚层,胚胎变成圆柱形及主要器官系统的雏形。另外,此期的胚胎发育对环境的影响十分敏感,在某些有害因素(如病毒、药物等)的作用下较易发生先天性畸形。第1周卵裂、胚泡形成与植入受精卵从输卵管向子宫方向的运行中,不断进行分裂、增殖的过程称为卵裂,卵裂产生的细胞称卵裂球。第一次卵裂是在受精后的30小时左右发生,以后每10几小时卵裂一次,第3天时形成一个由12—16个卵裂球构成的实心胚,称桑椹胚。桑椹胚继续细胞分裂并由     

对诱导因子的探索

受精卵经卵裂、囊胚期而到原肠期。近来很多发育生物学家对囊胚期在发育过程中的功能特感兴趣。一般认为,囊胚中期细胞具有化学的分化。原肠期开始有形态上的分化,背唇(Spemann的组织者)诱导外胚层形成脑、脊索及肌细胞等;中胚层和内胚层分区,自主分化产     

麦叶蜂的胚胎发育

麦叶蜂的胚胎发育在27℃恒温下7天完成。核的分裂迁移与胚盘的形成与一般昆虫相同。胎膜有两层:羊膜形成不久即破裂而退化,不形成背器,浆膜一直保留至孵化前。麦叶蜂的原肠形成由于胚带中央部分细胞的内陷,内胚屋(中肠基)位于两端。胚带一共分为19节,计头部5节(包括原头,但前上颚节不久消失,不具副器),胸部5节,腹部11节。触角最初位于口后,以后移至口前。上唇不成对,非副器。 麦叶蜂的胚带末端初弯向背面,当形成神经节及副器最发达时胚带缩短,以后其末端又弯向腹面,使整个胚带由卵的腹面迁至背面。当进行上述胚动时,胚带同时自首尾两端开始背合。 神经沟自口后开始,至尾端为止,由此而来的神经细胞形成腹面神经索,前脑中脑及视叶由口前的外胚层而来。侧单眼由视叶外面的外胚层发生内陷,形成网膜细胞,而表层的细胞即成为角膜细胞。胃肠神经系由前肠背面两个突起发展而来。 中肠由前肠及后肠末端两群内胚层细胞(中肠基)发育而成,后肠末端的凸起形成马氏管。 外胚层成对的内陷共有14对,头部的4对成为幕骨前臂、上颚内突、幕骨后臂及唾腺,中胸、后胸及腹部第1—8节者形成呼吸系统。酒色细胞为随同气管一起内陷的外胚层细胞,但形成后与体表失去联络。 血球主要来自中间中胚层,脏壁中胚层成为消化管的肌层,体壁     

白符(虫兆)胚胎发育的形态观察(弹尾纲:等节(虫兆)科)

对白符(Folsomiacandida)胚胎发育全过程进行显微观察,记述了白符从卵裂、囊胚期、原肠期、组织分化期、孵化前期等不同发育阶段的形态变化和发育过程。其结果表明,白符卵为聚产,形成大小不等的卵块,卵初产时为乳白色,卵壳表面覆盖有细密的颗粒状突起,直径为110—126μm。随着白符发育的进行,胚膜直径增大到180—185μm,其卵裂方式为完全均等卵裂,整个胚胎发育历期7—10d。     

胚胎中囊胚腔在原肠形成中的作用

两栖类卵受精后经过多次卵裂形成囊胚,在它的里面有一较大的腔,称为囊胚腔。腔内为分裂球分泌的液状物质,这种物质在四细胞时就在分裂腔中存在,随卵裂的进行分裂腔不断扩大。到囊胚期时腔内充满了这种蛋白样的液状物质。那么这种囊胚腔除了作为分裂球向内迁移提供一个空间的场所外,腔内的物质究竟有什么作用? 早在3e年代就证明,两栖类胚胎的囊胚液为碱性物质(pH9),这种碱性液体能减低细胞表面的界面张力,使细胞的局部:表面容易产生突起——伪足,认为这就是促使胚孔处内陷的     

Mechanism of an Alternate Type of Echinoderm Blastula Formation: The Wrinkled Blastula of the Sea Urchin Heliocidaris erythrogramma

While most indirect-developing echinoderms (possessing a feeding larval stage) form a hollow, smooth-walled blastula, most direct-developing species form a wrinkled blastula. The process of wrinkled blastula formation was examined in the direct-developing sea urchin, Heliocidaris erythrogramma . Approximately 5 hrs after fertilization the blastula epithelium contains folds along one, two or three orthogonal planes, which superficially appear like 2-, 4- or 8-cell stages, respectively. Microinjection of fluorescent dye into individual blastomeres of 2-, 4- and 8-cell embryos revealed that the wrinkles correspond with the first, second and third cleavage planes. Two factors appear to generate the wrinkled blastula epithelium. First, blastomeres undergo a partial separation along the first, second and third cleavage planes during early cleavage. Subsequent cell divisions are oriented such that the blastula epithelium is constructed with deep creases along these planes of cell separation. Second, there is no room for the expansion of the developing blastoderm within the tightly fitting fertilization envelope. Prior to hatching from the fertilization envelope, wrinkles in the blastula epithelium disappear, due to an increased packing and elongation of the cells. In addition, a substantial volume of cellular material is removed as lipids are secreted into the blastocoel in an apocrine fashion.     

Developmental expression of HpNanos, the Hemicentrotus pulcherrimus homologue of nanos

The Hemicentrotus pulcherrimus homologue of nanos (HpNanos), that encodes a protein containing two CCHC zinc finger motifs, was isolated from a gastrula cDNA library. The accumulation of HpNanos mRNA during embryonic development and the spatial expression pattern are reported. Developmental northern blot analysis revealed that HpNanos mRNA markedly accumulated during the blastula stages, and then decreased in abundance at the mesenchyme blastula stage. The second phase of HpNanos mRNA expression occurred during gastrulation, after which the expression returned to a low level. Whole-mount in situ hybridization showed that the HpNanos was exclusively expressed in four to six small micromere-descendant cells at the blastula stage. The expression of HpNanos was restricted to the coelomic pouch, which gives rise to the mesoderm of the ventral surface of the adult rudiment, at the prism stage. These results suggest that HpNanos expression will be instrumental for future analyses of the function of small micromere-descendant cells and of the origin of germ cells during sea urchin development.     

Free radical processes in the embryogenesis of Anura]

The localization of free radical processes and changes in their level during the common frog development have been studied by means of grafted copolymerisation and autoradiography. The maps of distribution of relative concentrations of free radicals were obtained for the beginning of cleavage, blastula, gastrula and neurula. The distinct regionalization was found in the beginning of cleavage: the concentration of the free radicals in the cortical layer and dorsal half of embryo is lower than in the central area and ventral half, resp. At the early blastula stage this regionalization is preserved in its general features. The region of embryo characterized by active free radical processes corresponds to the presumptive endo- and mesoderm in the period of inductive interaction. The possible participation of regional changes in oxidative metabolism in the fertilized egg in the determination of cytoplasmic localization of morphogenetic potencies is discussed. At the later stages there were variations observed in free radicals concentration, which are discussed as being related to the determination and morphogenesis of some rudiments of embryo. A local rise of free radicals concentration was also found out in the eye rudiment just before the onset of its components differentiation.     

The bases for and timing of regional specification during larval development in Phoronis

A fate map has been constructed for Phoronis vancouverensis. The animal pole of the egg gives rise to the apical plate in the hood of the actinotroch larva. The vegetal pole of the egg marks the site of gastrulation. During the initiation of gastrulation the cells of the animal pole of the embryo are directly opposite those at the vegetal pole of the embryo. The plane of the first cleavage always goes through the animal-vegetal pole of the egg. In about 70% of the cases the plane of the first cleavage is perpendicular to the future anterior-posterior axis of the actinotroch larva; in the remaining cases the plane of the first cleavage is either oblique with reference to, or occurs along, the future anterior-posterior axis of the larva. Following gastrulation catecholamine-containing cells first make their appearance in the apical plate and gut cells first produce esterase. The timing of regional specification in these embryos has been examined by isolating animal or vegetal, anterior or posterior, or lateral regions at different time periods between the initiation of cleavage and gastrulation and examining their ability to differentiate. Animal halves isolated from early cleavage through late blastula stages do not gastrulate and do not form catecholamine-containing cells. When animal halves are isolated with endoderm during gastrulation, they differentiate catecholamine-containing cells. Vegetal halves isolated at the 8- to 16-cell stage gastrulate and form normal actinotroch larvae with esterase-positive gut and catecholamine-containing apical plate cells. When this same region is isolated at blastula stages it does not gastrulate and does not differentiate these cell types. Vegetal halves isolated during gastrulation subsequently form esterase-positive gut cells, but they do not form catecholamine-containing apical plate cells. When presumptive anterior, posterior, or lateral halves are isolated from early cleavage through blastula stages, each half forms a normal actinotroch larva. Lateral halves isolated during gastrulation also form normal larvae. Anterior halves isolated during late gastrulation differentiate only the anterior end of the actinotroch larva. These isolates have a hood with catecholamine-containing apical plate cells and the first part of an esterase-positive gut but lack the anlagen of the intestine and protonephridia. Posterior halves isolated during late gastrulation differentiate only the posterior end of the actinotroch which lacks a hood with catecholamine-containing cells but has an esterase-positive gut, protonephridia, and the anlagen of the intestine.(ABSTRACT TRUNCATED AT 400 WORDS)     

达氏鳇不同发育期胚胎对低温的耐受研究

研究了达氏鳇12个发育期胚胎经过不同低温（2 ℃、3 ℃、5 ℃、7 ℃和8 ℃）处理12 h、24 h、2 d、3 d、6 d、10 d、15 d、20 d和30 d后的孵化率和仔鱼成活率.结果表明,卵黄栓期、隙状胚孔期、神经管闭合期胚胎在2～8 ℃水温下,处理24 h后孵化率为0;卵裂期、囊胚早期、原肠中期胚胎在2～8 ℃水温下,处理3 d后孵化率低于30%;囊胚晚期、原肠早期、眼基期、尾芽期、心跳期和尾达头部期胚胎在5～8 ℃水温下,处理3 d后孵化率、仔鱼成活率超过70%;随低温处理时间延长,胚胎和仔鱼的死亡率增加,处理时间与孵化率、仔鱼成活率呈负相关;囊胚晚期、原肠早期、眼基期胚胎在5 ℃水温下耐受力较强,处理10 d后孵化率、仔鱼成活率超过70%.本研究表明,达氏鳇胚胎发育过程中囊胚晚期、原肠早期和眼基期胚胎可以在某一低温下进行短期保存,其孵化率、仔鱼成活率与常温（16～17 ℃）下没有显著差异.这对于达氏鳇胚胎（受精卵）的长途运输有重要意义.     

Xoom is maternally stored and functions as a transmembrane protein for gastrulation movement in Xenopus embryos

Xoom has been identified as a novel gene that plays an important role in gastrulation of Xenopus laevis embryo. Although Xoom is actively transcribed during oogenesis, distribution and function of its translation product have not yet been clarified. In the present study, the polyclonal antibody raised against Xoom was generated to investigate a behavior of Xoom protein. Anti-Xoom antibodies revealed that there are two forms of Xoom protein in Xenopus embryos: (i) a 45 kDa soluble cytoplasmic form; and (ii) a 44 kDa membrane-associated form. Two forms of Xoom protein were ubiquitously detected from unfertilized egg to tadpole stage, with a qualitative peak during blastula and gastrula stages. Immunohistochemical examination showed that Xoom protein is maternally stored in the animal subcortical layer and divided into presumptive ectodermal cells during cleavage stages. Enzymatic digestion of membrane protein and immunologic detection of Xoom showed that Xoom exists as a membrane-associated protein. To examine a function of Xoom protein, anti-Xoom antibodies were injected into blastocoele of stage 7 blastula embryo. Anti-Xoom antibodies caused gastrulation defect in a dose- dependent manner. These results suggest that maternally prepared Xoom protein is involved in gastrulation movement on ectodermal cells.     

Ultrastructural Study of Changes in Cell Morphology and Extracellular Matrix in Prospective Endodermal Cells of Newt Embryos (Cynops pyrrhogaster) before and during Gastrulation

The cell morphology, cell-to-cell contact behavior and extracellular matrix (ECM) of inner cells (prospective endodermal cells) of newt ( Cynops pyrrhogaster ) embryos were examined from the morula to gastrula stage by light and electron microscopy. The inner cells showed increased cell-to-cell contact from the early blastula to early gastrula stage. The cells formed blebs (5–15 μm in diameter) during the blastula stage, and started to form filopodia and lamellipodia before gastrulation. Alcian blue and lanthanum nitrate treatment revealed ECM components on the cell surface in the early blastula stage and these components increased in amount from the late blastula to early gastrula stage. It is suggested that the increase in ECM components on the cell surface may have some relation with changes in cell-to-cell contact and formation of processes on the cell surface. Besides the cell surface ECM components, glycogen-like granules were observed in intercellular spaces. From the distribution of granules in gastrulae, it is suggested that these may be important in maintaining intercellular spaces for migration of invaginating cells.     

Overexpression of S-adenosylmethionine decarboxylase (SAMDC) activates the maternal program of apoptosis shortly after MBT in Xenopus embryos

Overexpression of S-adenosylmethionine decarboxylase (SAMDC) mRNA in 1- and 2-cell stage Xenopus embryos induces cell autonomous dissociation at the late blastula stage and developmental arrest at the early gastrula stage. The induction of cell dissociation took place "punctually" at the late blastula stage in the SAMDC-overexpressing cells, irrespective of the stage of the microinjection of SAMDC mRNA. When we examined the cells undergoing the dissociation, we found that they were TUNEL-positive and contained fragmented nuclei with condensed chromatin and fragmented DNA. Furthermore, by injecting Xenopus Bcl-2 mRNA together with SAMDC mRNA, we showed that SAMDC-overexpressing embryos are rescued completely by Bcl-2 and becometadpoles. These results indicatethat cell dissociation induced by SAMDC overexpression is due to apoptotic cell death. Since the level of S-adenosylmethionine (SAM) is greatly reduced in SAMDC-overexpressing embryos and this induces inhibition of protein synthesis accompanied by the inhibition of DNA and RNA syntheses, we conclude that deficiency in SAM induced by SAMDC overexpression activates the maternal program of apoptosis in Xenopus embryos at the late blastula stage, but not before. We propose that this mechanism serves as a surveillance mechanism to check and eliminate cells physiologically damaged during the cleavage stage.