scholarly journals OOCYTE DIFFERENTIATION AND VITELLOGENESIS IN THE ROACH PERIPLANETA AMERICANA

1964 ◽  
Vol 20 (1) ◽  
pp. 131-155 ◽  
Author(s):  
Everett Anderson
Keyword(s):  
Nuclear Envelope ◽  
Phase Contrast ◽  
Periplaneta Americana ◽  
Light And Electron Microscopy ◽  
Internal Surface ◽  
Follicle Cells ◽  
Growth Stages ◽  
Cytoplasmic Organelle ◽  
Last Stage ◽  
Oocyte Differentiation

The ovary of the roach Periplaneta americana has been studied by techniques of light and electron microscopy. Each ovariole (panoistic type) contains a linear array of oocytes in varying stages of development. Newly formed oocytes become encased by a layer of follicle cells and begin pinocytosis. All subsequent growth stages of the oocytes are dependent, in part, on this phenomenon. All of the pinocytotic caveolae show an unique surface modification; i.e., on their internal surface they have an amorphous or filamentous substance and their external surface is studded with many fine radially oriented spike-like projections. The pinosomes of early oocytes do not contain a demonstrable internal structure; they are thought to contain nutritive substances for the developing oocytes rather than yolk precursors. When the oocyte enters its last stage of growth, characterized by yolk deposition, the caveolae become filled with a dense material which is thought to be the precursors of yolk. Hence the conclusion is drawn that yolk formation is independent of any cytoplasmic organelle system of the oocyte and that the precursors of this deutoplasmic substance are manufactured outside the ovary and are internalized by the process of pinocytosis. Under the phase-contrast microscope the nucleoli of early oocytes are large irregular masses and show the phenomenon of nucleolar emission (fragmentation). These "emissions" become randomly dispersed in the nucleoplasm and some of them come to be intimately associated with the fenestrated nuclear envelope. After this process ceases, the main nucleolar mass becomes vacuolated. Electron micrographs suggest that the constituent particles of the nucleolar emissions migrate from the nucleus through patent pores of the nuclear envelope.

The eggshell of Drosophila melanogaster. II. New staging characteristics and fine structural analysis of choriogenesis

1986 ◽  
Vol 64 (10) ◽  
pp. 2152-2175 ◽  
Author(s):  
Lukas H. Margaritis
Keyword(s):  
Electron Microscopy ◽  
Light And Electron Microscopy ◽  
Dark Field ◽  
Posterior Pole ◽  
Follicle Cells ◽  
Vitelline Membrane ◽  
Simultaneous Formation ◽  
Last Stage ◽  
Flocculent Material ◽  
Factor C

The characteristics of the stages of choriogenesis have been identified using light and electron microscopy. Nine stages have been discerned (11A, 11B, 12A, 12B, 12C, 13A, 13B, 14A, 14B), replacing the four stages used so far (11, 12, 13, 14). Characteristics used to determine the stage of the choriogenesis include (a) the size of oocyte as compared with the whole follicle, (b) the length of the chorionic appendages, and (c) the fine structure of the chorionic layers at the main shell and at the specialized regions. Factors a and b were detected by dark-field light microscopy on living follicles, whereas factor c was studied with electron microscopy. At stage 11A the vitelline membrane has just been completed. At stage 11B the follicle cells secrete the wax layer and the respiratory appendages start to form. Stage 12A follicles secrete endochorion at the anterior pole and the appendages elongate, whereas at stage 12B the main shell follicle cells start to secrete endochorion complex. Stage 12C shows initiation of pillar formation at the main shell and 150 μm long appendages. Stage 13A is characterized by 200 μm long appendages and formation of endochorionic cavities at the main shell, through the participation of a "flocculent" material. At stage 13B the endochorionic "roof is formed, which is completed at stage 14A by the simultaneous formation of the "roof network." The last stage, 14B, exhibits 300 μm long appendages and the secretion of exochorion over the entire follicle. The above stages are accompanied by region-specific formation of specialized structures which include the respiratory appendages, the operculum, the posterior pole, the micropyle, and the collar.

Phase-contrast and electron-microscopic observations on a membranous complex in primary spermatocytes of the mouse

1975 ◽  
Vol 18 (1) ◽  
pp. 1-17
Author(s):  
A. Pleshkewych ◽  
L. Levine
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Phase Contrast ◽  
Cultured Cells ◽  
Light And Electron Microscopy ◽  
Cytoplasmic Inclusion ◽  
Electron Microscopic ◽  
Secondary Spermatocyte ◽  
Living Mouse ◽  
Circular Contour

A prominent cytoplasmic inclusion present in living mouse primary spermatocytes has been observed by both light and electron microscopy. It began to form at prometaphase and continued to increase in thickness and length as the cells developed. By metaphase it was a distinct sausage-shaped boundary that enclosed a portion of the cytoplasm between the spindle and the cell membrane. At the end of metaphase, the inclusion reached its maximum length. At telophase, it was divided between the daughter secondaries. The inclusion persisted as a circular contour in the interphase secondary spermatocyte. Electron microscopy of the same cultured cells that were previously observed with light microscopy revealed that the inclusion was a distinctive formation of membranes. It consisted of agranular cisternae and vesicles, and was therefore a membranous complex. Many of the smaller vesicles in the membranous complex resembled those found in the spindle. The cisternae in the membranous complex were identical to the cisternal endoplasmic reticulum of interphase primary spermatocytes. Nevertheless, the organization of vesicles and cisternae into the membranous complex was unique for the primaries in division stages, since such an organization was not present in their interphase stages.

Further observations on nucleolar tails in amphibian oocytes

1991 ◽  
Vol 99 (3) ◽  
pp. 515-521
Author(s):  
PEDRO LEÓN ◽  
JAMES KEZER ◽  
ERIC SCHABTACH
Keyword(s):  
Electron Microscopy ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Outer Surface ◽  
Light And Electron Microscopy ◽  
Nuclear Pores ◽  
Core Component ◽  
Amphibian Species ◽  
Attachment Structures ◽  
Convoluted Tubules

Large oocytes from some amphibian species possess beaded or unbeaded intranuclear tails that penetrate the extrachromosomal nucleoli through a distinct pit in their surface and attach to the central core component Here we show, using light and electron microscopy, that tails anchor nucleoli to the nuclear envelope through intricate attachment structures. These structures are composed of interconnected spherical masses containing highly convoluted tubules and associated extratubular proteins, directly directly in contact with the inner nuclear membrane. Fibers emerging from the nuclear pores seemingly hold the attachment complex in place. Beads on the nucleolar tails are formed by the accumulation of proteins on the outer surface of smooth tubules. The function of these intranuclear tubules is unknown

Inheritance of Intracellular Bacteroids in Periplaneta Americana

1973 ◽  
Vol 31 ◽  
pp. 510-511
Author(s):  
R. S. Daniel
Keyword(s):  
Periplaneta Americana ◽  
Uranyl Acetate ◽  
Follicle Cells ◽  
Serial Sections ◽  
Intercellular Spaces ◽  
Electron Microscopic ◽  
Electron Microscopic Data ◽  
Zone Ii ◽  
Germinal Tissue ◽  
Subsequent Literature

Blockmann was the first to assume that intracellular symbiotic bacteroids of blattids are transmitted to progeny through the ovaries of the parent. Subsequent literature has generally supported the transovariole transmission theory, but whether bacteroids infect differentiated oocytes or ovarian anlage has not been determined. This paper presents electron microscopic data relevant to the question of bacteroid inheritance.Ovaries of P. americana were fixed in cacodylate buffered glutaraldehyde and osmium then block-stained in uranyl acetate. Sections were stained with uranyl acetate and lead citrate. Serial sections (Fig 1 insert) of germaria (Zone II) reveal that bacteroids are absent in formative follicle cells (Fig 1), oogonia (Fig 2) and intercellular spaces of germinal tissue in adults and nymphs.

Mitosis in the Fission Yeast Schizosaccharomyces Pombe: A Comparative Study with Light and Electron Microscopy

1971 ◽  
Vol 9 (2) ◽  
pp. 475-507 ◽  
Author(s):  
E. KATHLEEN McCULLY ◽  
C. F. ROBINOW
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Nuclear Envelope ◽  
Schizosaccharomyces Pombe ◽  
Light And Electron Microscopy ◽  
Metaphase Plate ◽  
Middle Part ◽  
Mitotic Chromosomes ◽  
Nucleolar Material ◽  
Differential Expansion

Mitosis in Schizosaccharomyces pombe has been followed in living cells by phase-contrast microscopy and studied in fixed and suitably stained preparations by light microscopy. Successful preservation of nuclear fine structure in this yeast, not previously achieved, has allowed us to confirm and extend the observations made with light microscopy. Without first arranging themselves on a metaphase plate, mitotic chromosomes become grouped in 2 clusters radiating, finger-like, from 2 points of attachment at opposite poles of an elongating nucleus. At these 2 sites electron microscopy reveals the presence of disk-shaped electron-dense organelles which we have called kinetochore equivalents (KCE). At mitosis the KCEs are connected across the nucleus by a narrow bundle of parallel microtubules which we refer to as the spindle. Integration of our observations has led us to propose that at mitosis the separation of the KCEs and their attached chromosomes is initiated by a differential expansion of the nuclear envelope restricted to the region between recently divided KCEs and that expansion of the nuclear envelope later becomes general, resulting in a marked elongation of the nucleus. Displacement of the nuclear contents to the ends of the elongated nucleus gives it the shape of a dumbbell. The elongation of the microtubule bundle keeps in step with the elongation of the nucleus but does not appear to be the cause of it. It may have the function of keeping the separated KCEs rigidly apart. During mitosis the nucleolus persists and stretches out within the unbroken envelope of the nucleus as it elongates. Towards the end of division equal amounts of nucleolar material are found in the rounded ends of the dumbbell-shaped nucleus. The break up of the dumbbell shape into daughter nuclei seems to involve the breaking of its tenuous middle part and a pivoting of its 2 ends in opposite directions. In the course of our work on mitosis we have become aware of features in the cytoplasm of growing S. pombe cells which are described here for the first time. The cells invariably contain several prominent vacuoles containing an extremely electron-dense material which stains metachromatically with toluidine blue and may be polyphosphate. The mitochondria are of special interest for 2 reasons. First, because they have unique mesosome-like membrane invaginations and secondly, because a mitochondrion is regularly associated with the single KCE by the side of the interphase nucleus, as well as with each one of the 2 KCEs that occupy opposite ends of the intranuclear spindle during mitosis.

Ovulation and placentation in Botryllus schlosseri (Ascidiacea): an ultrastructural study

1987 ◽  
Vol 65 (5) ◽  
pp. 1181-1190 ◽  
Author(s):  
Giovanna Zaniolo ◽  
Paolo Burighel ◽  
Gianbruno Martinucci
Keyword(s):  
Light And Electron Microscopy ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Main Role ◽  
Botryllus Schlosseri ◽  
Maternal Origin ◽  
Cell Layers ◽  
Test Cells ◽  
Vitelline Coat

The mode of ovulation and placentation was studied by light and electron microscopy in the ovoviviparous ascidian Botryllus schlosseri using colonies from the laboratory. The full-grown oocyte is surrounded by the outer and inner follicle cell layers, the acellular vitelline coat (chorion), and the test cells, and it is furnished with its own vesicular oviduct which is interposed between the egg and the atrial epithelium. In contrast to most ascidians, the outer follicle is thick and has an ultrastructure consistent with intense protein synthesis. At ovulation the outer follicle shows signs of involution where it contacts the oviduct. When the oviducal wall breaks and the egg moves through the oviduct, the outer follicle cells are discharged in the mantle to form a sort of corpus luteum. The egg remains hanging in the atrial chamber by means of a cuplike "placenta." The placental tissues are all of maternal origin, being derived from both the atrial and oviducal epithelia together with some of the inner follicle cells. These latter anchor to the oviducal epithelium by means of junctional spots and a filamentous cementing secretion. Our results suggest that the main role of the "placenta" is to attach the embryo to the parent, thus exposing it to the flow of seawater.

scholarly journals UNE FORME MICROTUBULAIRE ET PARACRISTALLINE DE RETICULUM ENDOPLASMIQUE DANS LES PHOTOCYTES DES ANNELIDES POLYNOINÆ

1966 ◽  
Vol 31 (1) ◽  
pp. 135-158 ◽  
Author(s):  
J. M. Bassot
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Fine Structure ◽  
Nuclear Envelope ◽  
Contact Surface ◽  
Special Kind ◽  
The Other ◽  
Cytoplasmic Organelle ◽  
Specialized Form

Luminous cells of polynoid worm elytra have been examined by methods of electron microscopy, with special attention focused on the fine structure of photogenic grains. These cells send apical prolongations into the mid-part of the elytra. The plasma membrane is very sinuous, and a special kind of desmosome links two portions of the same membrane. In addition to all the organelles which can be found in nonluminescent epithelial cells of the elytra, numerous photogenic grains are contained in their cytoplasm. These grains are composed of undulating microtubules measuring 200 A in diameter; their disposition in the grain is highly regular, and the grains appear as paracrystals. At the borders of the grains, the walls of the microtubules are often in continuity with those of the endoplasmic reticulum and with the external membrane of the nuclear envelope. Because of this fact, the microtubules of the grains may be considered a cytoplasmic organelle, representing a specialized form of the endoplasmic reticulum. The microtubules permit the repartition, inside and outside their walls, of two different products, one being forty-three times more abundant than the other; thus, the contact surface, in comparison to the volume, is greatly increased. The induction of the luminous reaction by change in the permeability of the microtubule walls, allowing contact between the two substances, is suggested as a working hypothesis. There is an evolution of the grains along the axis of the photocytes. The grains are often surrounded by progressively increasing amounts of glycogen. Their paracrystalline disposition is altered at the apex of the luminous cells.

scholarly journals In cell architecture of the nuclear pore complex and snapshots of its turnover

2020 ◽  
Author(s):  
Matteo Allegretti ◽  
Christian E. Zimmerli ◽  
Vasileios Rantos ◽  
Florian Wilfling ◽  
Paolo Ronchi ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Mrna Export ◽  
Light And Electron Microscopy ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Formidable Challenge ◽  
Cellular Context ◽  
Pore Complexes

SummaryNuclear pore complexes (NPCs) mediate exchange across the nuclear envelope. They consist of hundreds of proteins called nucleoporins (Nups) that assemble in multiple copies to fuse the inner and outer nuclear membranes. Elucidating the molecular function and architecture of NPCs imposes a formidable challenge and requires the convergence of in vitro and in situ approaches. How exactly NPC architecture accommodates processes such as mRNA export or NPC assembly and turnover inside of cells remains poorly understood. Here we combine integrated in situ structural biology, correlative light and electron microscopy with yeast genetics to structurally analyze NPCs within the native context of Saccharomyces cerevisiae cells under conditions of starvation and exponential growth. We find an unanticipated in situ layout of nucleoporins with respect to overall dimensions and conformation of the NPC scaffold that could not have been predicted from previous in vitro analysis. Particularly striking is the configuration of the Nup159 complex, which appears critical to spatially accommodate not only mRNA export but also NPC turnover by selective autophagy. We capture structural snapshots of NPC turnover, revealing that it occurs through nuclear envelope herniae and NPC-containing nuclear vesicles. Our study provides the basis for understanding the various membrane remodeling events that happen at the interface of the nuclear envelope with the autophagy apparatus and emphasizes the need of investigating macromolecular complexes in their cellular context.

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