莫桑比克非鲫卵黄形成的电镜观察

运用透射电镜观察了莫桑比克非鲫卵母细胞的生长.根据卵母细胞的大小和内部结构特征,将其分为四个时期:卵母细胞生长早期:卵黄泡形成期:卵黄积累期:卵黄积累完成期.本文着重研究了主要卵黄成分--卵黄球的形成过程.卵黄球属外源性卵黄,由卵母细胞通过微胞饮作用吸收肝脏合成的卵黄蛋白原后形成的.在卵黄大量积累前,卵母细胞内的线粒体和多泡体聚集成团,构成卵黄核,继而线粒体大量增殖,线粒体形状发生改变,形成同心多层膜结构,为大量的卵黄物质积累提供场所.最终形成的卵黄球由被膜、卵黄结晶体和两者之间的非结晶区三部分组成.       

鸡胚卵黄球能否演变为胚胎细胞?

Ο.Б.勒柏辛斯卡娅认为跌入于胚下腔中的卵黄球能够演变为胚胎的内胚层细胞和进入于内外二胚层之间的卵黄球能够演变为血岛的这一假说近年来在细胞学和胚胎学界引起了激烈的争论. 我们从1954年春天开始研究这个问题,工作可分三方面:(1)分别观察鸡胚正常发生过程中的内胚层和血岛的形成过程和卵黄球的变化——包括鸡胚和鸭胚从未孵到孵育20天各期的胚胎和卵黄囊切片,采用各种主要的细胞学上的染色方法和卵黄球的活体染色观察.(2)卵黄球的离体和活体培养——培养材料包括未孵及孵育各期的胚盘下卵黄球.离体培养     

不同发育时期哲罗鱼卵黄的超微结构

应用透射电镜观察了不同发育时期哲罗鱼(Hucho taimen)卵黄的超微结构.根据哲罗鱼卵黄物质在卵母细胞中的加工合成、积累以及卵母细胞中参与卵黄颗粒形成的细胞器的变化,可将该鱼卵黄发生分为4个特征时期,即卵黄发生前期、卵黄泡期、卵黄积累期和卵黄积累完成期.卵黄发生前期是指卵母细胞发育过程中的卵黄物质开始积累前的时期,此时期核仁不断分裂,出现线粒体云和早期的滤泡细胞层、基层和鞘细胞层;卵黄泡期特点主要是细胞器不断变化产生卵黄泡和皮层泡;卵黄积累期的滤泡膜由内向外依次为放射带、颗粒细胞层、基层和鞘细胞层,此时外源性卵黄前体物质不断经过血液汇集于鞘细胞层,后经微胞饮作用穿过胶原纤维组成的基层,经过多泡体作用转运至颗粒细胞内,在细胞内经过加工和修饰形成小的卵黄蛋白颗粒,卵黄蛋白颗粒经微胞饮穿过放射带进入卵母细胞边缘形成的空泡中,不断积累形成卵黄球;进入卵黄积累完成期,卵黄球体积变大,向细胞中心聚集,填满大部分卵母细胞,卵黄积累完毕.     

日本血吸虫卵黄培养细胞超微结构动态的研究

从超微结构水平研究日本血吸虫卵黄细胞培养的动态。在体外培养过程中,卵黄细胞对外界环境的改变比日本血吸虫的其它体细胞更加敏感。随着培养时间的延长,卵黄细胞发生不同程度的变性,成熟卵黄细胞比未成熟卵黄细胞发生变性。变性主要表现在核和胞质的电子密度降低;卵黄球相互融合,或卵黄球与膜之间的空隙逐步增大,最终卵黄球从中释放出来,变成裸露体;脂滴数目增多,体积增大;粗面内质网扩大和囊泡变,其上的核糖体脱颗粒等     

鲫鱼卵发生过程中细胞学和细胞化学的研究

序言 1960年我们在研究鱼类催情作用的时候,曾详细地观察了鲫鱼卵在发生过程中细胞学和细胞化学的变化。结果发现有些和前人记载不一致的地方。尤其是卵黄球的来源、液泡和卵黄球的化学性质以及卵黄球和液泡之间的关系等问题引起了我们的注意。因为这些问题的阐明对细胞生理学有一定的意义。     

鸡卵黄DNA的存在、提取和特性分析

利用免疫细胞化学技术证实了鸡蛋卵黄球中DNA的存在 .利用Ficoll 40 0密度梯度离心纯化卵黄球并提取了DNA .限制性内切酶分析表明所得卵黄DNA是序列不均一的DNA分子群 .MspⅠ和HpaⅡ分析显示该DNA的甲基化程度极低 .Southern杂交表明卵黄DNA含有基因组DNA的一小部分序列 .并认为卵黄DNA是一种独特的有可能在鸡胚早期发育中发挥功能的DNA .     

中华大蟾蜍输卵管分泌物在受精过程中作用的探讨

未曾包被输卵管分泌物的卵球,即无胶膜卵球,在授与高浓度精液(0.9—3.8×10~8个精子/毫升)条件下,并不能受精,从而进一步证实,输卵管分泌物是卵球受精的必要因素。透射电镜观察表明,未曾接触输卵管分泌物的体腔卵球和体外排出卵球的卵黄膜中,有许多纤维束(直径1200—1500A),纵横交织。在输卵管中运行时,卵球外周包被输卵管分泌物。输卵管各部分(直部、卷曲前部和卷曲部)分泌物中,都含有松散卵黄膜纤维束的因子,经其作用,卵黄膜纤维束松散成微纤维(直径50一70A)。卵黄膜纤维束松散程度与胶膜作用时间的长短呈现正的相关性;卵黄膜纤维束松散程度与卵球受精率可能亦具有正的相关性。     

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.     

日本鬼鲉胚胎发育及仔、稚鱼形态学观察

对日本鬼鲉的胚胎及仔稚鱼形态发育进行观察,描述了各发育时期的发育时序和形态特征。日本鬼鲉的受精卵呈正圆球形,无色透明,无油球,平均卵径为(1.42±0.04)mm,呈浮性。在水温(22±0.5)℃,盐度31‰的条件下,历时约52h10min完成孵化。初孵仔鱼全长(3.04±0.13)mm,卵黄囊长(2.23±0.08)mm,卵黄囊高为(1.65±0.06)mm,在(21±0.5)℃水温下,仔鱼孵化后3d内营内源性营养(卵黄囊仔鱼),第4天卵黄囊完全消失,开口摄食轮虫。13d全长(7.12±0.35)mm,背鳍鳍条出现进入稚鱼早期,15d全长(7.92±0.61)mm鱼体及各鳍开始出现金黄色斑纹,25d全长(13.66±0.55)mm,整个鱼体呈黄褐色,完成变态进入幼鱼期,开始营底栖生活。同时观察了自胚胎发育至幼鱼期鱼苗体表色素分布的变化及其器官发育的形态变化。     

细角螺卵子发生的细胞学和超微结构的研究

利用组织切片和透射电镜观察细角螺卵细胞发育的显微和超微结构,结果表明:细角螺卵原细胞期细胞核体积较大,呈椭圆形,核膜明显且有不规则的凹陷,细胞质内出现大量的线粒体和高尔基体.根据卵黄颗粒物的多少和大小可将卵母细胞分为前、中、后三个时期:前期卵母细胞细胞核内染色质浓缩,核仁可见,并出现核周间隙;中期卵母细胞内细胞核移向细胞的一端,核内染色质仍呈高电子密度状态,核仁不明显或消失;后期卵母细胞内的细胞核受挤压形状变得不规则,细胞质内可见少量的线粒体,大量的卵黄颗粒聚集在细胞质中并融合成很大的卵黄球.成熟期卵母细胞卵黄物质多且有较大的脂滴.     

The origin of protein and fatty yolk in Rana pipiens. III. Intramitochondrial and primary vesicular yolk formation in frog oocytes.

The precise origin of the primary yolk precursor complex or primary vesicular yolk is obscure but in its earliest recognizable stage it is a typical multivesicular body which first acquires a moderately electron-dark matrix. Following this, an extremely electron-dark amorphous material, the yolk protein, appears within the precursor. This yolk protein increases in amount as the yolk vesicle grows and by the time the precursors are about 1 micrometer in diameter this protein is partly to almost completely crystalline. Yolk originating within mitochondrial cristae unlike that in the yolk precursor complexes is crystalline from its earliest appearance. Intracristae mitochondrial yolk crystals have a spacing of 70--85 A. Their molecular organization appears in some sections as electron-dark lamellae and in others as light cylinders surrounded by an electron-dark matrix.     

THE ORIGIN OF PROTEIN AND FATTY YOLK IN RANA PIPIENS : II. Electron Microscopical and Cytochemical Observations of Young and Mature Oocytes

Electron microscope studies of young oocytes have demonstrated that the plate-like, hexagonally shaped yolk bodies previously observed in living cells are wholly within the substance of oocyte mitochondria and that they remain within these mitochondria while increasing in size. These bodies possess a crystalline structure consisting of what appear to be lines, with a spacing of 70 to 85 A, and appear very dense in the electron microscope. After formalin fixation such bodies give an intense positive test for protein, and when viewed in the electron microscope are only slightly less dense than after OsO₄ fixation. Evidence is presented for the origin of these crystals within a single crista. The clusters of yolk globules previously studied in living cells are seen to consist of several types of bodies, but an irregular dense droplet predominates. This dense material is apparently secreted by small spherical bodies which, the evidence suggests, originate from the breaking up of filamentous mitochondria and which possess an outer double membrane and sometimes internal cristalike membranes. When thin sections of young oocytes are immersed in xylol the dense globules of the clusters are dissolved, but the hexagonal bodies are unaffected, indicating that the globules are of a predominantly fatty nature, while the hexagonal bodies are of a predominantly protein nature. Examination of mature or almost mature oocytes has revealed that the main body of the yolk platelets is crystalline in nature and is surrounded by a thick matrix which, in light microscope study, masks the fact that the face view of the main body of the platelets is often hexagonal. The spacing within the main body is found to be 70 to 85 A. The crystal laminae of this material can be resolved quite clearly into rows of particles. Dense globules of varying sizes are found in the cytoplasm between the platelets. When thin sections of these OsO₄-fixed oocytes are immersed in xylol, the material of the globules is extracted and the crystalline material of the platelets remains unaffected, indicating the fatty nature of the globules and the protein nature of the platelets. The platelets of the mature egg resemble the hexagon bodies, previously described in young oocytes, in their protein nature, their crystalline spacing, and their hexagonal outline. This is given as strong evidence for the origin of the mature platelets by the growth of the intramitochondrial hexagon bodies. The biochemical implications of this study are discussed.     

The Presence of Intramitochondrial Yolk-crystals in Oocytes of Hypophysectomized Bullfrog Tadpoles*

Ovaries of hypophysectomized Rana catesbeiana tadpoles. weighing I to 14 g, were prepared for electron microscopic study. The oocytes are at the growth phase, ranging from 50 to 190 μm in diameter. The observation on these oocytes has revealed the presence of intramitochondrial yolk-crystals but not cytoplasmic yolk platelets. The crystalline structure, situated within the intracristal space, consists of a hexagonal array of dense particles about 50 Å in diameter and 72 Å in periodicity. Our data agree with those reported in oocytes of intact ranid species. According to literatures, crystals of intramitochondrial yolk and of cytoplasmic yolk platelets show similar ultrasturctures. The precursor of cytoplasmic yolk platelets in adult Xenopus oocytes is known to be synthesized in the estrogen-stimulated liver and incorporated via circulation into oocytes by gonadotropin-dependent micropinocytosis. The present finding suggests that the intramitochondrial yolk could be formed within oocytes, independently of the pituitary control.     

The origin of protein and fatty yolk in Rana pipiens. V. unusual paracrystalline configurations within the yolk precursor complex

Three unusual highly ordered configurations of yolk protein in yolk precursor bodies are described. These differ from the crystalline structure of the main body of mature yolk platelets. One of these is an aggregation of paired membranes with a spacing of about 100 Å between the members of a pair. The paired membranes of such an aggregation may be straight, parallel, and very close together; they may appear as a tight whorl; or they may display an intermediate random arrangement with varying distances between pairs. Another configuration is a tubule with a diameter of about 450 Å, whose wall appears in cross section to consist of particles measuring 50 × 100 Å. A third configuration is a crystalline array of rows of angular-shaped particles with a spacing of about 160 Å. It is suggested that these may represent intermediates in the transition of vitellogenin to lipovitellin and phosvitin.     

Incorporation of 35S-sulfate into yolk platelets of Xenopus laevis embryos. A study using electron microscope autoradiography.

Inorganic 35S-sulfate was injected into Xenopus laevis embryos before first cleavage to study incorporation of the label into the yolk platelets in order to localize glycosaminoglycan synthesis. Electron microscope autoradiography of embryonic thin sections from blastulae and gastrulae revealed that the primary site of label incorporation is at the edge of the yolk platelets, and, to a lesser extent, in their interiors. Autoradiography of isolated yolk platelets, lacking unit membranes, indicated the absence of label. Thus, edge associated label comes from the yolk platelets membrane, and interior label is solubilized in the glycerol-water gradient during yolk platelets isolation. Ruthenium red staining of yolk platelet in situ shows haavy deposits of the dye on the yolk platelet membrane surface facing the cytoplasmic surface. The crystalline main body of isolated yolk platelets does not take up the dye. It appears that continuous synthesis or sulfation of glycosaminoglycan occurs primarily at the outer surface yolk platelet membranes during early development, providing a novel site for this process.     

STUDIES ON AMPHIBIAN YOLK : 2. The Isolation of Yolk Platelets from the Eggs of Rana pipiens

Previous methods which employed simple sucrose or salt solutions to isolate yolk platelets have failed to preserve their superficial layer, and the preparations obtained generally exhibit some contamination when observed with the light or electron microscope. When yolk platelets are suspended in a sucrose-polyvinylpyrrolidinone medium, however, they remain relatively intact and their superficial layer is not lost to the medium. A method, which takes advantage of this fact, is described for the isolation of frog (Rana pipiens) yolk platelets which are free from nuclear contamination and practically free from cytoplasmic contamination. After such platelets are treated with distilled water, the superficial layer is no longer seen and a new dense and granular matrix is frequently found surrounding the crystalline main body. The significance of this and other observations concerning the effects of calcium and ethylenediamine tetraacetate are discussed.     

Yolk organelles and their membranes during vitellogenesis ofXenopus oocytes

Summary The yolk platelets ofXenopus laevis have been studied by thin-section and freeze-fracture electron microscopy to characterize the boundary membrane during yolk formation. Throughout vitellogenesis, large yolk platelets are in close contact with smaller nascent yolk organelles. Two types of primordial yolk platelets (I and II) have been discriminated. After membrane fusion these precursors can be completely incorporated into the main body of existing platelets, numerous yolk crystals then merge and form one uniformly stratified core. Lipid droplets are tightly attached to the membrane at all developmental stages of yolk platelets. A direct connection of endoplasmic reticulum to the membranes of yolk platelets was not observed. On freezeetching replicas, yolk-platelet membranes present fracture faces with intramembranous particles (IMP) of various sizes and a heterogeneous distribution of approximately 200–600 IMP/μm² at the E face, and 1200–2100 IMP/μm² at the P face. Again, this presentation of the membrane exhibits neither anastomoses to the endoplasmic reticulum, nor caveolae that exclude the uptake of yolk-containing vesicles into these yolk organelles. Proteinaceous yolk platelets tend to fracture along their periphery through the superficial layers.     

Incorporation of 35S-Sulfate into Yolk Platelets of Xenopus laevis Embryos

Inorganic ³⁵S-sulfate was injected into Xenopus laevis embryos before first cleavage to study incorporation of the label into the yolk platelets in order to localize glycosaminoglycan synthesis. Electron microscope autoradiography of embryonic thin sections from blastulae and gastrulae revealed that the primary site of label incorporation is at the edge of the yolk platelets, and, to a lesser extent, in their interiors. Autoradiography of isolated yolk platelets, lacking unit membranes, indicated the absence of label. Thus, edge associated label comes from the yolk platelets membrane, and interior label is solubilized in the glycerol-water gradient during yolk platelets isolation.
Ruthenium red staining of yolk platelet in situ shows heavy deposits of the dye on the yolk platelet membrane surface facing the cytoplasmic surface. The crystalline main body of isolated yolk platelets does not take up the dye.
It appears that continuous synthesis or sulfation of glycosaminoglycan occurs primarily at the outer surface yolk platelet membranes during early development, providing a novel site for this process.     

YOLK PROTEIN UPTAKE IN THE OOCYTE OF THE MOSQUITO AEDES AEGYPTI. L

Yolk proteins are thought to enter certain eggs by a process akin to micropinocytosis but the detailed mechanism has not been previously depicted. In this study the formation of protein yolk was investigated in the mosquito Aedes aegypti L. Ovaries were fixed in phosphate-buffered osmium tetroxide, for electron microscopy, before and at intervals after a meal of blood. The deposition of protein yolk in the oocyte was correlated with a 15-fold increase in 140 mµ pit-like depressions on the oocyte surface. These pits form by invagination of the oocyte cell membrane. They have a 20 mµ bristle coat on their convex cytoplasmic side. They also show a layer of protein on their concave extracellular side which we propose accumulates by selective adsorption from the extraoocyte space. The pits, by pinching off from the cell membrane become bristle-coated vesicles which carry the adsorbed protein into the oocyte. These vesicles lose the coat and then fuse to form small crystalline yolk droplets, which subsequently coalesce to form the large proteid yolk bodies of the mature oocyte. Preliminary radioautographs, and certain morphological features of the fat body, ovary, and midgut, suggest that the midgut is the principal site of yolk protein synthesis in the mosquito.