Fine Structure of the Nucleolus in Normal and Mutant Xenopus Embryos

1967 ◽  
Vol 2 (2) ◽  
pp. 151-162
Author(s):  
ELIZABETH D. HAY ◽  
J. B. GURDON
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Xenopus Laevis ◽  
Fibrous Material ◽  
Osmium Tetroxide ◽  
Wild Type ◽  
Granular Component ◽  
Basic Dyes ◽  
Fibrillar Component ◽  
Xenopus Laevis Embryos

Mutant and normal Xenopus laevis embryos (0-nu, 1-nu, 2-nu) were examined in the electron microscope after glutaraldehyde and/or osmium-tetroxide fixation. During cleavage both 0-nu and wild-type embryos contain multiple small nucleolar bodies, less than 1 µ in diameter, composed mainly of a fibrous material. By the end of cleavage or beginning of gastrulation, granular caps develop on the fibrous nucleolar bodies. In 1-and 2-nu cells, the multiple nucleolar bodies are replaced during gastrula and neurula stages by definitive nucleoli (2-5 µ in diameter) which contain abundant small (150 Å) granules intermingled with fibrous material. In 0-nu cells, one or two pseudonucleoli (1-3 µ in diameter) appear at about the same time that definitive nucleoli develop in wild-type cells. The multiple small nucleolar bodies disappear as the pseudonucleoli enlarge. Pseudonucleoli differ from definitive nucleoli in having a much smaller amount of the granular component, which is located as a cap on the periphery of the fibrous component and not mingled with it. The granular component of the 0-nu pseudonucleoli, however, is not distinguishable in its fine structure from the same component of normal nucleoli. In many 0-nu tadpoles at stage 41, the granular component of the nucleolus is entirely absent and the fibrillar component is very prominent. Both granular and fibrous components of the 0-nu pseudonucleoli contain RNA as judged by RNase sensitivity and staining affinity for basic dyes.

scholarly journals THE FINE STRUCTURE OF THE RAT CEREBELLUM

1964 ◽  
Vol 23 (2) ◽  
pp. 277-293 ◽  
Author(s):  
Robert M. Herndon
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Light Microscope ◽  
Osmium Tetroxide ◽  
Granule Cells ◽  
Cell Types ◽  
Bergmann Glia ◽  
Rat Cerebellum

This paper describes the fine structure of the granule cells, stellate neurons, astrocytes, Bergmann glia, oligodendrocytes, and microglia of the rat cerebellum after fixation by perfusion with buffered 1 per cent osmium tetroxide. Criteria are given for differentiating the various cell types, and the findings are correlated with previous light microscope and electron microscope studies of the cerebellum.

Lipid in Erysiphe graminis hordei and its possible role during germination

1970 ◽  
Vol 16 (11) ◽  
pp. 1041-1044 ◽  
Author(s):  
W. E. McKeen
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Osmium Tetroxide ◽  
Erysiphe Graminis ◽  
Glutaraldehyde Fixation ◽  
Sudan Black B ◽  
Erysiphe Graminis Hordei ◽  
Sudan Iv ◽  
Mother Cells ◽  
Hyphal Tip

Osmiophilic bodies appear in parts of the colonial growth of Erysiphe graminis DC. f. sp. hordei Em Marchal culture CR3 growing on the susceptible commercial Keystone variety of barley. They are readily observed by the light and electron microscope after osmium tetroxide staining and are abundant in conidiophores, conidia, and mycelium except in haustorial mother cells, in which they are usually absent. The metabolism of haustorial mother cells is distinct and the fine structure of adjoining cells is frequently different. Osmiophilic bodies are absent from the growing hyphal tip, but gradually increase in number and size further back in the terminal cell. Electron micrographs show that they are intracytoplasmic, intravacuolar, and up to 1 μ in diameter. When the colony is washed with acetone or alcohol rather than with aqueous buffer, after glutaraldehyde fixation, before osmium tetroxide fixation, the osmiophilic bodies are removed, indicating that they are lipids. Fat stains, Sudan black B, and Sudan IV stain these bodies. Perhaps the water needs of the germinating conidium are met in part by the oxidation of fats.

scholarly journals Latrophilin2 is involved in neural crest cell migration and placode patterning in Xenopus laevis

2019 ◽  
Vol 63 (1-2) ◽  
pp. 29-35
Author(s):  
Natsumi Yokote ◽  
Marianna Y. Suzuki-Kosaka ◽  
Tatsuo Michiue ◽  
Takahiko Hara ◽  
Kosuke Tanegashima
Keyword(s):  
Cell Migration ◽  
Xenopus Laevis ◽  
Neural Crest ◽  
Neural Crest Cell ◽  
Wild Type ◽  
Neural Crest Cell Migration ◽  
Guidance Molecule ◽  
G Protein Coupled ◽  
Crest Cell ◽  
Xenopus Laevis Embryos

Latrophilin2 (Lphn2) is an adhesion-class of G protein-coupled receptor with an unknown function in development. Here, we show that Xenopus laevis lphn2 (Xlphn2) is involved in the migration and differentiation of neural crest (NC) cells and placode patterning in Xenopus laevis embryos. Although Xlphn2 mRNA was detected throughout embryogenesis, it was expressed more abundantly in the placode region. Morpholino antisense oligonucleotide-mediated knockdown of Xlphn2 caused abnormal migration of NC cells, irregular epibranchial placode segmentation, and defective cartilage formation. Transplantation of fluorescently-labeled NC regions of wild-type embryos into Xlphn2 morpholino-injected embryos reproduced the defective NC cell migration, indicating that Xlphn2 regulates the migration of NC cells in a non-cell autonomous manner. Our results suggest that Xlphn2 is essential for placode patterning and as a guidance molecule for NC cells.

scholarly journals Electron Microscopy of Retinal Photoreceptors

1960 ◽  
Vol 7 (3) ◽  
pp. 493-497 ◽  
Author(s):  
Arnaldo Lasansky ◽  
Eduardo de Robertis
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Electron Microscope ◽  
Outer Segment ◽  
Osmium Tetroxide ◽  
The Other ◽  
Rod Outer Segments ◽  
Outer Segments ◽  
Retinal Photoreceptors ◽  
L1 And L2

The fine structure of the cone and rod outer segments of the toad was studied under the electron microscope after fixation in osmium tetroxide and fixation in formaldehyde followed by chromation. In the OsO4-fixed specimens, the rod outer segment appears to be built of a stack of lobulated flattened sacs, each of which is made of two membranes of about 40 A separated by an innerspace of about 30 A. The distance between the rod sacs is about 50 A. The sacs in the cone outer segment are originated by the folding of a continuous membrane. The thickness of the membranes and width of the spaces between the cone sacs is the same as in rod, but the sac innerspace is slightly narrower in the cone (∼ 20 A). After fixation in formaldehyde and chromation, two different dense lines (l1 and l2) separated by spaces of less density appear. One of the lines, l1, has a thickness of 70 A and is less dense than the other, l2, which is 30 A thick. The correlation of the patterns obtained with both fixatives is considered and two possible interpretations are given. The possibility that l2 is related to a soluble phospholipid component is discussed. It is suggested that the outer segments have a paracrystallin organization similar to that found in myelin.

scholarly journals STUDIES ON CILIA

1963 ◽  
Vol 18 (2) ◽  
pp. 345-365 ◽  
Author(s):  
Peter Satir
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Cross Section ◽  
Osmium Tetroxide ◽  
Freshwater Mussel ◽  
Structure And Function ◽  
Spring Water ◽  
Fine Structure And Function ◽  
And Function ◽  
Active Preparation

Upon excision into spring water, the lateral cilia of the gill of the freshwater mussel Elliptio complanatus (Solander) stop beating, but 0.04 M potassium ion can activate the gill so that these cilia again beat with metachronal rhythm. One per cent osmium tetroxide quickly pipetted onto a fully activated gill fixes the lateral cilia in a pattern that preserves the form and arrangement of the metachronal wave, and permits the cilia to be studied with the electron microscope in all stages of their beat cycle. Changes are seen in the fixed active preparation that are not present in the inactive control, i.e., in the packing of the cilia, the position of the axis of the ciliary cross-section, and the diameter of the ring of peripheral filaments. Analysis of these parameters may lead to new correlations between ciliary fine structure and function.

Bacterioids in the Rectal Organ of the Lantern Dug Pyrops Candelaria Linn (Homoptera: Fulgoridae)

1996 ◽  
Vol 54 ◽  
pp. 806-807
Author(s):  
W.W.K. Cheung ◽  
J.B. Wang
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Osmium Tetroxide ◽  
Uranyl Acetate ◽  
Sodium Cacodylate Buffer ◽  
Lead Citrate ◽  
Sodium Cacodylate ◽  
Special Pair ◽  
Adult Females ◽  
Cacodylate Buffer

The lantern bug harbours three symbionts, namely a, x and i in its body. These microorganisms are supposed to be transmitted transovarially to the future progeny. The x-symbionts are found in a special pair of organs called the x-organ which bulges to form a rectal organ in adult females. The purpose of this study is to investigate into the fine structure of the x-symbionts. This will serve as a basis for understanding the interactions of this microorganism with its host.The rectum of the lantern bug Pyrops candelaria Linn, was dissected out in buffered insect saline and fixed in 2.5% glutaradehyde in 0.1M sodium cacodylate buffer (pH 7.2) for 1 hr. The rectal organ was subsequently post-fixed in 1% osmium tetroxide (pH 7.2) and dehydrated in alcohol/acetone series. These were blocked in Spurr resin and cut with a Reichert Ultratome. Sections were stained with uranyl acetate and lead citrate and examined with a JEOL JEM-1200EX electron microscope. Thick sections (1 μn) were stained with 1% toluidine blue and examined under a Nikon Optiphot light microscope.

scholarly journals FINE STRUCTURE OF THE LARVAL ANURAN EPIDERMIS, WITH SPECIAL REFERENCE TO THE FIGURES OF EBERTH

1961 ◽  
Vol 10 (3) ◽  
pp. 425-435 ◽  
Author(s):  
George B. Chapman ◽  
Alden B. Dawson
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Free Surface ◽  
Electron Microscope ◽  
Fibrous Material ◽  
Distal Region ◽  
Epidermal Layer ◽  
Basal Plasma Membrane ◽  
Basal Plasma ◽  
Ultrathin Sections

Small pieces of skin from 8 cm long Rana clamitans larvae were fixed in OsO4, washed, dehydrated, and embedded in a methacrylate mixture. Ultrathin sections were cut on a Porter-Blum ultramicrotome and were examined in an RCA electron microscope, type EMU 2D. The sections showed that aggregates of fibrous material in the cells of the inner layer of epidermal cells are identical in disposition and size with the classical figures of Eberth. It is conclusively shown that these figures do not arise from an aggregation of mitochondrial filaments. The tendency of the fibrils to concentrate on attachment points, or thickenings of the basal plasma membrane, is noted. It is also observed that numerous mitochondria are located in the distal region of the cells of the outer layer of epidermis in association with the secretory vacuoles. Microvilli are seen occasionally on the free surface of the skin. Cisternae are found only in the cells of the outer epidermal layer, while vesicular endoplasmic reticulum is found in the cells of both epidermal layers.

scholarly journals THE ULTRASTRUCTURE OF GLIOSOMES IN THE BRAINS OF AMPHIBIA

1965 ◽  
Vol 26 (2) ◽  
pp. 313-322 ◽  
Author(s):  
Zbigniew Srebro
Keyword(s):  
Electron Microscope ◽  
Xenopus Laevis ◽  
Osmium Tetroxide ◽  
Rana Esculenta ◽  
Lamellar Structures ◽  
Dense Bodies ◽  
Constant Structure ◽  
Granular Matrix

Small fragments of superficial neuropil and fragments of deeper layers from various regions of the brains of Xenopus laevis Daud. and Rana esculenta L. were fixed in buffered osmium tetroxide, embedded in Vestopal W or methacrylate, and studied with the electron microscope. The glial fibers and their meningeal end-feet contain numerous large mitochondrion-like dense bodies for which the term "gliosome" has been adopted. Gliosomes have a specific and constant structure characterized by the presence of a row of peripheral and circular canaliculi and an electron-opaque fibrous or finely granular matrix. Also, another less frequently found type of gliosome is present which contains regular lamellar structures. The gliosomes vary considerably in size and may be very large, up to 9 µ in length. Numerous and various intermediate forms between mitochondria and gliosomes can be seen. Gliosomes are largest and most numerous in the distal portions of the glial fibers and in the meningeal end-feet.

scholarly journals ON THE FINE STRUCTURE AND COMPOSITION OF THE NUCLEAR ENVELOPE

1961 ◽  
Vol 11 (3) ◽  
pp. 559-570 ◽  
Author(s):  
R. W. Merriam
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Nuclear Envelope ◽  
Pore Structure ◽  
Potassium Permanganate ◽  
Osmium Tetroxide ◽  
Rana Pipiens ◽  
Total Density ◽  
Thin Sections ◽  
Whole Mounts

Nuclei from nearly ripe eggs of Rana pipiens were isolated and cleaned in 0.1 M KCl. The whole nucleus was then digested to various degrees with ribonuclease or trypsin, followed by washing and fixation in either osmium tetroxide or potassium permanganate. The nuclear envelope was dissected off, placed on a grid, air dried, and compared with undigested controls in the electron microscope. Some envelopes were dehydrated, embedded in methacrylate, and sectioned. Annuli around "pores" are composed of a substance or substances, at least partially fibrillar, which is preserved by osmium but lost during permanganate fixation. Material within the "pores" is also preserved by osmium but partially lost after permanganate. No evidence of granules or tubules in the annuli was found in air dried mounts although a granular appearance could be seen in tangentially oriented thin sections. Thin sections of isolated envelopes give evidence of diffuse material within the "pores" as well as a more condensed diaphragm across their waists. In whole mounts of the envelope the total density within "pores" is relatively constant from "pore" to "pore." All material within "pores," including the condensed diaphragm, is removable by trypsin digestion. Wispy material from the "pore" structure projects into the nucleus and annular material extends into the cytoplasm. Both annular and diaphragm materials remain with the envelope when it is isolated and are thus considered a part of its structure, not merely evidences of material passing through. There is no evidence of ribonuclease-removable material in any part of the "pore" complex.

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